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Jeff d
06-06-2014, 08:55 PM
I had another thread on this subject but I figured it would be best to start a new write-up/How To thread.

If you feel like reading through the other thread it's here:
http://www.mastercraft.com/teamtalk/showthread.php?t=60338

I struggled with random Medallion gauge and MDC issues for the last 4 years (Since I bought the boat). The tach would drop to 0 RPM while running and stop counting hours, the temp gauge would peg to 240+ degrees then go back to normal after a “reboot” (Super scary the first 2 times) then stopped working completely and the fuel gauge never worked right. All connections were triple checked and cleaned with no improvement. I never could gather enough concrete evidence to make me comfortable that it was definitively either the MDC or the gauges themselves even working through the Medallion troubleshooting guide. The MDC is about $290+ shipping and individual gauges that matched mine never really showed up on eBay and if they had they would have been used and still not necessarily “known good”. There were full sets available new from later year models for a few hundred bucks but there’s so much mystery around this electronic bus system that it was hard to know for sure if they’d work with the older MDC. Pretty much anyway I went on this would have been a bit of a gamble so I decided to go with the cheapest gamble of them all: Eliminate the middle man (The MDC) and go with an aftermarket set of analog gauges. I had heard anecdotal reports of this being a pretty easy project but hadn’t been able to find a write-up or anything.

Changing gauges in general is a bit of a painful process which will take around 2-3 hrs to complete even if you were swapping in OE gauges. Swapping in aftermarket analog gauges and eliminating the MDC adds about 45 mins to an hour to this job to re-work the wiring harness. So, it’s about a 3, maybe 4 hour job depending on your familiarity with dealing with such things.

So, here’s what worked for me. Some of this might be specific to the 1st gen Maristar 230 VRS/X-30 but it’s probably close on just about any of the boats of 2000-2005ish. The pre 2000 boats didn't have an MDC or Medallion gauges so, although I haven’t seen behind their dashes, we’re electrically duplicating the setup that the older boats would have.

Parts/Supplies:
-Set of analog gauges for standard American Marine senders. I chose Faria KTF001 which is a 6 gauge set of white faced gauges. I had no need for the speedometer as I have Perfect Pass but it’s cheaper to buy the set with the speedometer than to buy the 5 gauges I needed individually. I paid $172.12 shipped. Teleflex or any other brand should work just as well.
-5-6 waterproof heatshrink 1/4” female “quick connects”
-14-16 waterproof heatshink #10 ring terminals
-2 heatshrink butt splices
-Small zip ties
-1/4” heatshrink tube

Tools:
-Small socket set or wrench set for removing nuts on gauges. Sizes varied but 3/8” was the largest.
-Wire Cutters
-Crimpers
-Lighter to shrink the tubing/crimp connectors
-Multimeter (Optional but you probably want to check to make sure your boat’s wire colors and what not are the same as mine)

1) Disconnect the battery’s negative cable
2) Remove the gauge panel:
Lie under the dash looking up and get comfortable. You're about to contort your arms and work by feel for about 5-10 minutes while being very uncomfortable. Reach up into the cavity behind the gauges and feel around. You should be able to locate 8 wing nuts that are threaded onto studs on the back of the gauge panel. Look at the stud locations in step 4 to get an idea. Each will have a very tiny lock washer and a larger fender washer behind the wing nut. Try to grab them when you remove the nut but if things fall down in there you can retrieve them after the gauge panel is removed. After you have all 8 wing nuts removed you should be able to pull the gauge panel off with all of the gauges on it.

Alternatively you can first remove the whole vinyl coated fiberglass dash by removing those wing nuts but I found that that's much more of a pain vs. just reaching for the wing nuts if all you need to access is the gauges themselves. I’ve done this at least 4-5 times now.

3) Disconnect all gauges and check engine light and remove the gauge panel. These are all removable connectors so no need to cut anything yet.
http://www.mastercraft.com/teamtalk/attachment.php?attachmentid=112498&stc=1&d=1402101670
4) Swap your aftermarket gauges on the panel. This is pretty self-explanatory. The new tach had a little selector where I had to select the right position for an 8 cylinder engine.
http://www.mastercraft.com/teamtalk/attachment.php?attachmentid=112500&stc=1&d=1402101670
5) Cut off all of the 5 pin gauge connectors where the old gauges connected. This is the point of no return.
http://www.mastercraft.com/teamtalk/attachment.php?attachmentid=112499&stc=1&d=1402101670
6) Remove the yellow wire from the harness or just tape/heatshrink them and leave them in. This is the signal/bus wire and is no longer needed. I chose to remove it and “rebuild” the harness (More on that later)
7) Disconnect and remove the MDC. There are some short adapter pigtails for the 18 pin connector and the 5 pin connector. I just left those adapter pigtails on the MDC. If not using a speedometer plug or remove the pitot tube (unless you like wet feet/carpet)
8) Remove the plastic wire loom from the MDC harness
9) Pull the MDC and gauge harness up through the hole in the dash (Where the gauge panel normally resides)
http://www.mastercraft.com/teamtalk/attachment.php?attachmentid=112501&stc=1&d=1402101665
10) Cut off the connector with the gray, pink, tan, light blue, etc wires (The upper one in the picture above). I'll refer to this as the "MDC Harness" from here on.
11) Extend the tan wire over to the temp gauge position
12) Extend the gray wire over to the tach position
13) Extend the light blue wire over to the oil pressure gauge position
14) Extend the pink wire over to the fuel gauge position
Note: On steps 10-13 there was way more wire in the factory harness than I would need. I did not need to add any additional wire for any of this project. The orange wire is not used. Cut it off/coil it up and tape or heat shrink it off so it doesn't ground out.
15) Cut off the gauge harness connector with the black/yellow stripe, red/white stripe, etc. wires on it (The lower one in the pic above). I'll refer to this as the "Gauge Harness" from here on.
16) Butt Splice the black wire (Ground) from the MDC harness to the black/yellow stripe wire from the Gauge Harness.
17) Butt splice the purple wire (Ignition switched +12v) from the MDC harness to the red/white stripe wire from the Gauge Harness.
Note: Steps 16 & 17 are necessary because with the MDC in place ground and ignition switched power were passed through the MDC. With that removed you need to re-complete those circuits. I had a few feet of extra wire between them that was removed during that process as the wire didn’t need to go down to the MDC on the kick plate and then back up to the gauges.
http://www.mastercraft.com/teamtalk/attachment.php?attachmentid=112502&stc=1&d=1402101665
18) Strip and crimp on a 1/4” female on each dark blue wire in the gauge harness. This is tied into the NAV light switch and is for the gauge face backlights. There were warnings on the gauges to not allow this wire to touch the sender signal wire so I opted to put heat shrink over the terminal itself to insulate it from adjacent terminals.
19) Crimp #10 ring terminals on each Black/Yellow Stripe (ground), Red/White Stripe (ignition switched power), and the appropriate signal wire for that gauge position (i.e. gray for tach, pink for fuel, tan for temp, light blue for oil pressure). The volt meter doesn’t have a “signal” wire just +, - and + for backlight
20) Clean up your harness and prepare to reinstall the gauges. I had to re-terminate power and tach signal for my Perfect Pass as those were previously spliced in further down the line. I put heat shrink over the speedo wires since I wasn't installing it and the PP doesn't use those.
http://www.mastercraft.com/teamtalk/attachment.php?attachmentid=112504&stc=1&d=1402101665
21) Connect all gauges per the instructions
22) Reconnect battery and test basic function
23) Close everything up by reversing the process in step 2

I tested by running it at home and all of my gauges work now except the fuel level. I apparently have a bad fuel level sender on top of everything else as when I test it with a multimeter it shows 270 ohms (i.e. very empty) regardless of fuel level (It’s supposed to be 33.5 ohms full and 240 ohms empty). I’ll be replacing that sender and I’ll hopefully be done with gauge issues for a few years. If nothing else at least this setup is 50% easier to troubleshoot without the MDC in the mix. It’s either the sender or the gauge now. With the MDC/Medallion setup with any “gauge” malfunction it could be the MDC, the gauge, the sender or even another gauge causing “noise on the bus”.

Technically this should work fine for the 2006+ newer boats too but with the billet and molded plastic dash panels you may have cosmetic issues making these look right. I’ll leave that up to some of you guys with the fancier boats to figure out. I’m also unsure if ballast gauges would come into play on those boats as well.

Although completely unrelated to the MDC my depth sounder was generally unreliable. I replaced it with a matching one in the process.

The look and feel of the gauges is of similar quality to the OE Medallion gauges. I think the overall look has been improved in the process for my particular boat. Now everything matches. I'll report back when I have the new sender installed and I've done an actual water test.

In the end it cost me about $185 with the terminals and what not (Not counting depth sounder or the broken fuel sender) to replace my 5 gauges. I likely can sell the unused speedometer and pitot kit to recoup some of that cost. That's over $100 cheaper than just the MDC or an old stock set of medallion gauges and certainly cheaper than gauges + MDC by a large margin.

Before:
http://www.mastercraft.com/teamtalk/attachment.php?attachmentid=112505&stc=1&d=1402101665

After:
http://www.mastercraft.com/teamtalk/attachment.php?attachmentid=112507&stc=1&d=1402101665

After with engine running and backlights on:
http://www.mastercraft.com/teamtalk/attachment.php?attachmentid=112506&stc=1&d=1402101665

This little guy was instrumental in making this project take as long as possible:
http://www.mastercraft.com/teamtalk/attachment.php?attachmentid=112608&stc=1&d=1402330704

geordie-wake
06-07-2014, 01:28 PM
very informative thread which will prove useful when I get round to replacing mine, and they look great BTW

HRC
06-08-2014, 03:51 PM
Nice work. The new gauges look great.

supturb89
06-08-2014, 04:51 PM
Great job! If I'm ever working on the boat and my son catches wind of it he's always right there. I can't tell you how many times he's gotten in the way, but he does make it more enjoyable sometimes.

Jeff d
06-11-2014, 08:39 PM
Swapped in a new Wema 10" fuel level sender per a recommendation in a post from another member (eBay $35 shipped). Everything works now for the first time since I've owned the boat (4+ years)!

19_Skier
06-12-2014, 06:45 AM
great how-to write up and the final setup looks great. Enjoy the new/working gauges!

Jeff d
07-25-2014, 01:07 PM
I left it on eBay for a few weeks and finally sold the speedometer for $30. I thought I'd get more but that brings the total cost for the new gauges to $142.12 plus a few bucks for crimp connectors. That doesn't count the depth sounder but that system is unrelated to the MDC and wouldn't need replacement unless it happened to be bad too.

ac505
07-26-2014, 12:01 PM
Looks as if I am going to have to follow in your steps sometime soon. All the gauges packed in for about 30 mins then came back to life. Interestingly when cycling the ignition the gauges were twitching so my guess a duff gauge is causing all the others not to read. Intermittent problems are the worst to deal with, so I think my time is best spent updating to analogue. Winter project I think.

JohnnyB
07-27-2014, 09:41 AM
Questions on original setup...

Paddle wheel speedometer setup?

Did your tach have integrated depth guage?

Sent from my SCH-I435L using Tapatalk

Jeff d
07-27-2014, 09:58 AM
Questions on original setup...

Paddle wheel speedometer setup?

Did your tach have integrated depth guage?

Sent from my SCH-I435L using Tapatalk

No, it was a pitot speedometer. No integrated depth gauge. It was separate and didn't match from the factory.

JohnnyB
07-27-2014, 10:09 AM
Where did you find the color codes for MDC input such that you knew how to fan out to appropriate guages?

If I did the same, would likely go to GPS speedometer.

Very cool how-to that will benefit many.

Thanks.

Sent from my SCH-I435L using Tapatalk

Jeff d
07-27-2014, 10:16 AM
I found the wire colors in the MDC troubleshooting guide. It's covered in the other thread I linked in the OP.

ProStar Slalom
02-01-2015, 07:38 PM
We bought our '01 in 2007. In 2008 I had to replace the MDC box because I didn't know anything about "winterizing" it, and it was damaged by water from the speedo tubes. A couple of years later I had to replace the oil pressure gauge. Last season I was having issues with both the fuel gauge and the voltage gauge. It was probably the fuel gauge causing issues with the volt gauge...but hard to troubleshoot.

Anyway, followed Jeff's lead this weekend and replaced the entire set with analog gauges. I got the Faria gauge set shipped for about $130. Since I had an open spot where the "blank gauge" was, I added a Faria depth gauge while I was at it. All are working well. Thanks to Jeff for the great how-to write-up.

For anyone still dealing with Medallion, I have gauges for sale. All gauges are working fine, except for fuel and voltage...not sure about them.

Jeff d
02-01-2015, 07:53 PM
Noice! Did you have to replace the fuel level sender or did the original one work? I never definitely determined if my oe sender was bad or just non-standard/not compatible.

ProStar Slalom
02-01-2015, 08:01 PM
Noice! Did you have to replace the fuel level sender or did the original one work? I never definitely determined if my oe sender was bad or just non-standard/not compatible.

Jeff, my sender was bad as well. I assume the bad sender made for a bad signal to the fuel gauge...and for whatever reason was causing the voltage gauge to read bad as well. You can see on the medallion gauges that neither fuel nor voltage gauges would reset. Glad I'm done with them, and thanks again!

Jeff d
02-01-2015, 09:10 PM
Did you use an OE 3 wire solid state sender or a 2 wire mechanical sender?

Jayhawk
02-02-2015, 12:37 AM
We bought our '01 in 2007. In 2008 I had to replace the MDC box because I didn't know anything about "winterizing" it, and it was damaged by water from the speedo tubes. A couple of years later I had to replace the oil pressure gauge. Last season I was having issues with both the fuel gauge and the voltage gauge. It was probably the fuel gauge causing issues with the volt gauge...but hard to troubleshoot.

Anyway, followed Jeff's lead this weekend and replaced the entire set with analog gauges. I got the Faria gauge set shipped for about $130. Since I had an open spot where the "blank gauge" was, I added a Faria depth gauge while I was at it. All are working well. Thanks to Jeff for the great how-to write-up.

For anyone still dealing with Medallion, I have an MDC and gauges for sale. The MDC is fine, and has never had speedo tubes attached since I was worried about water damage. All gauges are working fine, except for fuel and voltage...not sure about them.

How much do you want for the MDC? Mine works fine, but it probably wouldn't hurt to have a spare.

76S&S
02-02-2015, 08:32 AM
Jeff D, great write-up. Not sure if I'm ready to tackle this yet as most of my gauges work, but do you still have your original tach? If so I may be interested if the part number matches mine.

Jeff d
02-02-2015, 09:00 AM
Jeff D, great write-up. Not sure if I'm ready to tackle this yet as most of my gauges work, but do you still have your original tach? If so I may be interested if the part number matches mine.

I have it but I wouldn't bother with it as it was one of the gauges that I had erratic behavior with.

76S&S
02-02-2015, 09:07 AM
10-4, thanks

ProStar Slalom
02-02-2015, 08:17 PM
Did you use an OE 3 wire solid state sender or a 2 wire mechanical sender?

I found an OE 3-wire on Ebay. Didn't want to mess with changing the wiring back there. Not many of these left; next one will be mechanical I'm sure.

Jeff d
02-02-2015, 09:05 PM
Ok, I guess mine was bad then. Good to know it will work with a standard gauge.

ProStar Slalom
02-13-2015, 06:41 PM
Ok, I guess mine was bad then. Good to know it will work with a standard gauge.

Follow-up. I thought I was good to go with OE 3-wire, but not so much. I was getting a signal to the gauge but only a small needle movement. Not sure why it wouldn't work since it's supposed to send the normal resistance range.

Anyway, switched to a 2-wire with a float and all is well. So for those who may be making the switch down the road...a 2-wire sender might need to be part of your plan.

Bohmer410
05-18-2015, 01:42 PM
Great Write-up!! Do you have any tips when reassembling the dash on, how to get to nuts back on the studs easily?

Jeff d
05-18-2015, 01:46 PM
Great Write-up!! Do you have any tips when reassembling the dash on, how to get to nuts back on the studs easily?

Not really. It's a pain. You have to be good at working by feel only.

Scot
06-19-2015, 01:03 AM
Great job. I sold my Stars and Stripes with good old analog gauges. Now dealing with medallion issues. Thinking of doing the same but will have to fabricate a new panel as my Sanger is set up for 5 inch gauges. (Sorry I'm a traitor to MC). My question is regarding the sending units. Sounds like the stock units are compatible with analog gauges maybe with the exception of fuel? I am so fed up with medallion. My tach is broken, only available through a dealership, and on back order. The other gauges work intermittently and you have to knock on the MDC every so often to get them to work. Connections are good, it's the unit itself. So unnecessary IMO.

Tsumi
06-19-2015, 02:09 AM
You would have to change out all of the gauges. All of them are fed with the digital signal from the MMDC, speedometer, RPM, oil pressure, temp, etc.

Oops, misread your post. Yeah, it seems like the stock sending units are fine. The fuel may or may not be fine, I think that has more to do with whether or not the fuel sender is functional or not. If it's still functional, I think it would be fine to continue using. If not, replace it with the float one.

Jeff d
06-19-2015, 08:00 AM
The jury is still out on the fuel level sender. The oem centroid senders that MC have a terrible reputation to begin with. I'm pretty certain that a couple of years before I did the MDC-extomy I connected an ohm meter up to my centroid sender and it worked just as expected in the standard range. At some point between then and when I did the gauge swap it seems to have failed. The guy on the Supra forum didn't mention that he needed a new fuel level sender.

In either case the bolt pattern on the tanks is pretty standardized across the board and a Wema SS sender can be had for as little as $35 shipped (depending on the length you need). I'd just factor that into your budget and buy it if you need it after testing with the original sender. The Wema does need shorter screws than the centroid though so be aware of that. If you run screws in there that are too long they'll blow out the bottoms of the little pockets cast in the plastic of the tank. Then you'll be more likely to have leaks when fuel sloshes around and splashes up on there.

CC2MC
07-15-2015, 06:07 PM
Jeff D, I noticed that the tach doesn't have the hour meter on there. What are you doing about that? I know PP has an hour meter on it, but it probably doesn't match up either, i'm guessing.

Jeff d
07-16-2015, 08:07 AM
Jeff D, I noticed that the tach doesn't have the hour meter on there. What are you doing about that? I know PP has an hour meter on it, but it probably doesn't match up either, i'm guessing.

Perfect pass has an hour meter and it can be synced up with actual hours. None of the tachs I've seen have provisions to roll them forward to match actual hours. Faria makes an identical tach to what I installed but with an hour meter but it's not available as part of a set. It would have cost quite a lot more to get the tach with the hour meter so I've opted just to use the one on my perfect pass.

paintpollz
07-20-2015, 07:07 PM
so what does the MDC actually do, besides cause issues for most people. And if you remove the MDC, what functions will you lose? I have a bad speedometer and a bad fuel gauge, but strangely enough the speed on the PP works fine. Thinking about making the switch with Jeff Ds nice writeup.

Jeff d
07-20-2015, 09:33 PM
It converts the standard variable resistance signals from the senders to a proprietary electronic bus signal to be processed by proprietary gauges. You don't lose any functionality if you replace the gauges with those that offer the same features of your existing gauges. I lost my tach hour meter in the process because I didn't want to spend the extra money to get a tach with an hour meter. I instead use the hour meter on my perfect pass (buried in the menus but it's there).

paintpollz
07-20-2015, 09:40 PM
It converts the standard variable resistance signals from the senders to a proprietary electronic bus signal to be processed by proprietary gauges. You don't lose any functionality if you replace the gauges with those that offer the same features of your existing gauges. I lost my tach hour meter in the process because I didn't want to spend the extra money to get a tach with an hour meter. I instead use the hour meter on my perfect pass (buried in the menus but it's there).

thank you jeff.

do you happen to know if my speedo will be plug and play with this? it shares the paddle wheel pickup with the PP. I'm assuming its just another harness to clip off behind the dash but I would like to double check. The reason why I'm contemplating this is my current regular speedo doesnt work, but my PP one does, not sure why. As you stated before its not really needed if you have the PP, but it just bugs the hell out of me that it is there and doesn't work. the fuel gauge is also funky and I know the sender is good, so I'm assuming my MDC is on its way out.

If all I have to do is order the gauges and new fuel sender, I think this is a great $250 fix and I'll be able to sleep knowing I've gotten rid of that MDC.

Jeff d
07-21-2015, 08:06 PM
I'm not sure on the paddle wheel. Does it currently go through the MDC? You'll have to get a paddle wheel compatible speedometer for sure since the ones included in most gauge sets are pitot pickup which work off water pressure rather than electrical impulses.

paintpollz
07-21-2015, 09:36 PM
I'm not sure on the paddle wheel. Does it currently go through the MDC? You'll have to get a paddle wheel compatible speedometer for sure since the ones included in most gauge sets are pitot pickup which work off water pressure rather than electrical impulses.

not sure if it goes thru the MDC. maybe someone else can chime in on that. I only assumed so because in your thread you mention a speedometer wire that you didn't use, obviously because you are running a GPS system. So my assumption was that wire was used on my system for both the PP and the regular speedo.

I'm willing to do this on a Saturday once the fall hits and document in this thread. Just trying to gather the BOM at the most reasonable cost.

paintpollz
07-28-2015, 10:43 PM
anyone know of an electronic speedo gauge for us paddle wheel guys? just cough up the $99 for the faria GPS one?

also, does anyone know if the factory paddle wheel speedo runs thru the MDC? I'm thinking it does since my PP gauge works (assuming it doesn't run thru the MDC) and the factory electronic speedo doesn't.

tommurtha
08-10-2015, 08:25 PM
Hi Neighbor, I'm in South Windsor. Your speedo failure probably is not mmdc related. My boat bought used had one not working and I had one delivered bad after the box was dropped. Have you unplugged and plugs the connection at the speedo.

paintpollz
08-11-2015, 09:49 PM
Hi Neighbor, I'm in South Windsor. Your speedo failure probably is not mmdc related. My boat bought used had one not working and I had one delivered bad after the box was dropped. Have you unplugged and plugs the connection at the speedo.

Hello there! negative on the unplugging and plugging. What is the purpose of unplugging the speedo? I'm assuming the connection to the speedo is fine although i admit i have not checked. It gauge sweeps and lights up, so I have no reason to believe that the connections are bad. That is why I was assuming that it was the signal that is coming out of the MMDC and not corrosion. I'm also assuming that the gauge actually does get a signal from the MMDC......

to be honest I don't even know how the speedo gauge works on this. I've been trying to figure this out for a while but no one seems to chime in.

Can someone on this forum confirm that the speedo gauge gets the signal from the MMDC? Because I know the PP picks up the signal direct from the same paddle wheel.

tommurtha
08-11-2015, 10:40 PM
If you remind me in case I forget I believe I have a spare speedo that I know works. I would be willing to let you borrow it to test with some collateral since I don't know you. My spares are in the Berkshires and I only go there on weekends. As for the connection I assumed you might have a bad wire in, there are 4, or maybe one pin is corroded . When I was having gauge issues Medallion sent me an MMDC troubleshoot procedure. You are welcome to it if you email me.

tommurtha
08-11-2015, 10:43 PM
What does gauge sweep mean/ Mine does not move on start up, either one. What is your failure mode? Not reading at all? Did it ever work?

paintpollz
08-17-2015, 04:00 PM
What does gauge sweep mean/ Mine does not move on start up, either one. What is your failure mode? Not reading at all? Did it ever work?

the gauge has never read since I bought the boat. It never moves up and down with the boat while under way. Occasionally it will read random fixed speeds, sometimes if you are looking at the right time you can watch it fall from 35mph ish to 0, but it acts as if it is picking up completely random signals from the MMDC.

The gauge sweep is at initial started, the gauges sweep from right to left.

Every other gauge is working in the boat. The fuel gauge sucks but everyone's fuel gauge sucks.

tommurtha
08-17-2015, 05:41 PM
Mine don't sweep but they all work. See email

paintpollz
08-19-2015, 07:52 AM
Perfect pass has an hour meter and it can be synced up with actual hours. None of the tachs I've seen have provisions to roll them forward to match actual hours. Faria makes an identical tach to what I installed but with an hour meter but it's not available as part of a set. It would have cost quite a lot more to get the tach with the hour meter so I've opted just to use the one on my perfect pass.

My PP is older and does not have an hour meter in it.

Can you even get a signal to an hour meter if you bypass the MMDC? I may pony up for the hour meter/tach combo.....

paintpollz
08-25-2015, 09:09 AM
My PP is older and does not have an hour meter in it.

Can you even get a signal to an hour meter if you bypass the MMDC? I may pony up for the hour meter/tach combo.....

bump on this question.

CruisinGA
08-25-2015, 09:31 AM
Any generic (not made for use with MMDC) tach with an hour meter can be made to work.
Just hook it to a battery before install to match current hours.

paintpollz
08-28-2015, 04:49 PM
Any generic (not made for use with MMDC) tach with an hour meter can be made to work.
Just hook it to a battery before install to match current hours.

Looks like I'm going to need about 25 days on a battery. better get moving.

thanks cruisinGA.

razorback64
09-07-2015, 05:05 PM
Having the same issues as everyone else - looking strongly at your fix. I'm always torn between old stuff that worked and new technology. Looks like Medallion may have been B'leading edge.
I have paddle wheel perfect pass that works great - only issue is my old eyes have trouble seeing the PP speed reading in bright light. Can I tie an independent speedo dial into the PP without adversely affecting it?

wakescene
08-02-2016, 12:45 AM
HUGE HUGE HUGE Props to Jeff for this write-up. I just recently completed this work on my 2001 Maristar 210VRS. WOW, what a difference. S--t just works now. I did have a host of other issues not specifically related to this swap, but was all wiring related. I ended up in the long run swapping out all of my switches, breakers and upgrading some wiring in the process.
I too ran into the Fuel-Sender issue as mentioned, but that will be resolved soon.

If anyone needs another resource for info on this procedure, please feel free to PM me. Its not that difficult, just TIME CONSUMING, so be prepared. Also be prepared to experience fiberglas shards a plenty working under the dash...MC didn't soften the edges of any holes during the building process.

Lastly, If you boat in Saltwater like I do, you are best to get very familiar with the electrical system of the 5+yr old boats. The corrosion gets into places you might never expect and will mess up even the most secure looking contact or connection.

Thanks again Jeff, you have done many of us a great service by your original post!

Kevin

CheeseSteak1
08-02-2016, 10:04 AM
What about the alarms that run through the MMCD? Do we loose all these with this conversion?

CruisinGA
08-02-2016, 10:09 AM
What about the alarms that run through the MMCD? Do we loose all these with this conversion?

I don't believe any alarms run through the MMDC. I am not 100% but I think the check engine light and audible alarms are triggered by the ECM.

Jeff d
08-02-2016, 10:16 AM
I can confirm that none of that runs through he MDC. The check engine light and the beeper both connect directly to the engine's computer as CruisinGA suggests.

After 2.5 seasons with my MDCectomy I can say without reservation that the MDC/Medallion bus gauges is really a useless system with no redeeming quality. It was a "solution" looking for a problem that didn't exist... Unless the problem was that the analog gauges were too easy for the lay person to understand and troubleshoot and the solution was to incorporate complexity into a system to increase dealer service revenues.

lakedawg
08-02-2016, 10:40 AM
No, only 12V, ground and sensor wires run through MMDC using standard sensor wire colors.

The 4 wires that run to the Medallion gauges are 12V, ground, nav and yellow for the signal wire. The signal wire is converted from ohms to volts by the mdc.

The blue nav wires are wired directly to the light switch

CruisinGA
08-02-2016, 10:44 AM
It was a "solution" looking for a problem that didn't exist... Unless the problem was that the analog gauges were too easy for the lay person to understand and troubleshoot and the solution was to incorporate complexity into a system to increase dealer service revenues.

Jeff my rationalization for the MMDC design was that MC often looks to push the envelope and try "new" for the sake of "new." I think the MMDC falls in this category. Digital guages were new and different in a boat and I'm sure the needle sweep and "ticking" at reset probably seemed cool to new boat buyers at the time. Just turned out to be an unreliable system!

Looking forward to swapping my gauges soon.

Jeff d
08-02-2016, 10:54 AM
Jeff my rationalization for the MMDC design was that MC often looks to push the envelope and try "new" for the sake of "new." I think the MMDC falls in this category. Digital guages were new and different in a boat and I'm sure the needle sweep and "ticking" at reset probably seemed cool to new boat buyers at the time. Just turned out to be an unreliable system!

Looking forward to swapping my gauges soon.

It wasn't just MC though. It seems that almost all inboard boat manufacturers went to the Medallion system around 2000. Malibu, Correct Craft, et al used the Medallion system. It probably was a combination of Medallion having good marketing/sales teams, offering compelling pricing, and whoever was in charge of gauge related decision making at the boat manufacturers not really evaluating what functionality and/or value the system was offering over the analog gauges they were replacing.

I hadn't considered the gauge "salute" after key on as a potential deal maker. That is a "feature" that you do indeed lose by going to analog gauges.

I prefer conspiracy theories!

CruisinGA
08-02-2016, 11:18 AM
It wasn't just MC though. It seems that almost all inboard boat manufacturers went to the Medallion system around 2000. Malibu, Correct Craft, et al used the Medallion system.
I prefer conspiracy theories!

I forgot that other manufacturers used the system as well! Conspiracy theory wins

wakescene
08-07-2016, 12:09 AM
I actually view the MDC as the precursor to the full-digital read-out gauges you are seeing today. Kind of like the way Microsoft used Vista as the stepping stone for Win7(I'm a computer guy). The MDC worked ok, but like Jeff said, it was a solution to a non-existing problem at the time. I also believe it was a sales/marketing effort too. They would brand the gauges for the manufacturer. Faria would probably loved the opportunity to brand the gauges for MC or any other, and maybe even do. (I did no research on that...so I got nothin)

Kelley97
01-17-2017, 08:42 PM
Used this last week. Thanks for doing the research for us. Made it all pretty easy.

Fullpass
01-18-2017, 12:13 PM
From Wakescene: "I actually view the MDC as the precursor to the full-digital read-out gauges you are seeing today."

I was looking at Livorsi gages...instead using a MDC OR MMDC...the Livosi gages can use information now directly from the newer style ECM...this eliminates the MDC OR MMDC altogether..ah ha...So the next question how can we upgrade our ECMS. But yes to the precursor of technology, WAKESCENE was right on.

Jeff d
01-18-2017, 12:41 PM
.the Livosi gages can use information now directly from the newer style ECM...this eliminates the MDC OR MMDC altogether..ah ha...So the next question how can we upgrade our ECMS.

I'm not familiar specifically with what you're referring to but it probably is like automotive gauges where they read CAN bus data from the ECU (MEFI in this case) and respond appropriately. My first thoughts would be that it would be an unnecessarily complex project with no real benefits.

First of all, most of the senders on this generation of boats don't run through the MEFI computer at all. It's crude relative to automobile ECUs of similar vintage. So, the computer doesn't have any clue what the specific temperature of the block is, the speed of the boat, the fuel level, the oil pressure, etc. It would know RPM and battery voltage but that's it. If the MEFI doesn't know what the conditions are then it obviously can't communicate that to a gauge for display to the operator. Conditions on these older fuel injected boats are monitored by the ECU with simple binary switches attached to various points on the engine. Then there are separate senders that communicate the "rich data" regarding those conditions (e.g. actual oil pressure PSI, water temperature in degrees, etc. through variable resistors) directly to the MDC/guages and the MEFI doesn't even know they exist.

So, you have an oil pressure switch that is in one condition when oil pressure is "OK" and another condition when it's "Bad". If it's low, the switch trips and the MEFI is like "oh crap, we have an oil pressure condition" and takes whatever action it's been programmed to take (e.g. illuminate "Check Engine" light, retard performance, shut down, whatever) but it doesn't know how many PSI the pressure is to even begin to send that data to a gauge. Then, there's a completely separate oil pressure sender that varies based on actual pressure but it's connected straight to the MDC and never stops to visit the MEFI. Same for the temperature.

Even if you could swap in a newer generation MEFI (Can you even get one for a 5.7L GM?) you'd have to get all of the appropriate senders and wire them up to feed said MEFI the data on all of the conditions... and it still has a layer of abstraction from the discrete senders so you'd re-gain almost all of the negatives of the MDC.

clvanasch
01-31-2017, 08:22 AM
Hey Jeff. I was going through your instructions last night to perform an MDC delete on my 2003 Mastercraft Maristar 210 and hit a bit of a road block. My wiring harness seems to be a bit different. Do you or anyone else on here have experience doing this on an 03 Maristar? As a side note, I installed a new Perfect Pass stargazer last year and utilize the plug and play harness as well so I want to make sure I keep that functional. Thank you for any help you can offer!

Keith2230
01-31-2017, 08:41 AM
I think you have a newer version of the MDC. Does this help? https://www.mastercraft.com/teamtalk/showthread.php?t=76720

clvanasch
01-31-2017, 09:30 AM
Hey Keith, Thanks for the information. I did find this diagram and it matches what I have on my MDC input. Which wire in this 24 pin connector is used for the RPM? Is it the pin 6 orange ang black wire? None of them are gray like Jeff describes in his write up. Also I'm not sure what wire I should use for the engine temp either. I appreciate your help!

outoftheoffice
03-05-2017, 07:39 PM
Jeff - huge thanks for the write-up. I did the same thing on my 2003 X-30 this weekend and your instruction was instrumental in getting it done right. I installed Faria Euro gauges and will post some better before/after photos soon. A couple wires along the way didn't match: 1) the ignition powered wire was found to be red/stripe instead of the purple mentioned, and 2) I didn't have a gray tach wire anywhere but I was able to track/find it upstream in the wire harness where it was picked off for the Perfect Pass, so I spliced into that location and ran a short segment of wire from there directly to the tach to make it work.

Unfortunately it sounds like I'm still having the same issue clvanasch has. Hopefully my description above can help to find the tach wire since I also couldn't find it in the MDC input connector, but I'm having 0 luck finding the temp sensor wire anywhere. I looked at the MDC input linked above (great info, thanks!) and it doesn't mention the temp sensor. When I finished my install I was left with two wires: one was kind of a lime green/tan and the other was maybe orangish with a dark stripe. They are the two wires hanging over the steering column at the bottom of the photo. I tried connecting each one to the temp gauge - one did nothing and the other just made the gauge quickly skip up and down a little bit. Voltage on the wire that did nothing was almost 12V and the skipping wire was between 3 and 4 volts. I know it can take a while for the temp to come up to something measurable so I even idled the motor for a while until it definitely felt warm enough to at least register the low end of the gauge (100F). I also briefly connected the oil pressure signal wire to the temp sensor to confirm the gauge was functioning (it was).


http://i297.photobucket.com/albums/mm219/outoftheoffice/IMG_2740.jpg

clvanasch
03-06-2017, 08:31 AM
Hey there. Man I have been working on this MDC feels like all winter. This weekend I finally got all the Faria gauges installed and found that the battle is not over...

I believe you and I have the same gauge and MDC harness. I had the same issue with the gray wire being back up stream and also the missing temp wire. I contacted Medallion and they told me that the RPM and temp is actually sent from the ECM to the MDC via a single black serial wire. Well, MC was nice enough to run the gray wire to the dash area for perfect pass which you can tap into but they did not run a dedicated temp wire... And also the temp sensor at the engine is a two pole sender going directly to the ECM. So what I ended up doing was adding another temp sender which was a single pole on the engine block and running a single wire up to the new temp gauge. This single pole sender measures ohms to ground. So I have all that in place and tested with a volt meter, BUT last night when I fired up the gauges for the first time, the temp gauge was still not working. I did not have time to really investigate further but tonight I will verify the gauge is actually functioning by jumping the temp signal lead to ground and making sure the indicator maxes out. I also think I received a defective volt meter gauge from Faria because it does not budge when I fire up the engine and I triple check the wiring and leads on the gauge with a volt meter. I guess I will get to see how Faria customer service is and how good of a warranty they have.

Fullpass
03-06-2017, 12:31 PM
MMDC TROUBLE GUIDE info on a lot of pin connectors

revised pdf ~ no longer half to look at pdf side ways...much better

outoftheoffice
03-06-2017, 02:01 PM
clvanasch, good to know I'm not alone in this boat (pun INTENDED!) What a bummer to hear about the temp sensor but I feel like it's somewhat expected as I thought I had read the ECM had a part in the sequence with the temp sender since it needed to know when the engine was overheating. I just hoped like Jeff encountered the temp was still being sent to the MDC, not intermixed into the ECM.

So, there's no way to pick the signal directly from the stock temp sensor and run an independent wire up the dash? Where did you decide to install your secondary temp sensor? And which one did you go with? Any photos would be a huge bonus! Did you fire up the engine to verify the tamp gauge was working? Reason I ask is because for some reason all my other gauges jump up a little when I turn the ignition on, except the temp gauge. I figured it was maybe because the nature of that sender and maybe not registering a temp yet? Bummer to hear about the volt gauge - that one should be the easiest of all of them to hook up and verify functionality.

On a related topic, have you tackled the fuel gauge yet? I still have the stock sender in my tank and my gauge reads E. As I understand it we'll need to swap to a two wire fuel sender? I tried grounding out my wiring at the sender and my gauge jumper to F, so I know the gauge works, but I just thought I had read the stock three wire sender wouldn't work with this replacement analog gauge?

clvanasch
03-06-2017, 02:39 PM
It does feel good to know someone else is struggling through this. I know my local mastercraft dealer is really getting tired of me calling them so I will be glad when this MDC delete is behind me! I searched all over hoping to find a temp wire to tap off of near the dash.

I've attached some photos. One pic is from the existing 2 wire sensor. Unfortunately, this is the only temp sensor on my block. Luckily on the other side of the block next to the terminate housing, there is a capped threaded hold where I put this sender. I just picked up one from West Marine. I can give you the exact part number when I get home but I still don't have this functioning so maybe I need to buy a faria specific sender. The sender is only $20 so I figured it was worth a try. The guy at west marine said they are pretty universal an most gauges use the same resistance scale. Yes I ran the engine for 5 minutes and the temp gauge did not budge from cold.

I can't believe the easiest and one gauge that has always worked on my boat now does not... I have a call into Faria and waiting for a return call so they can tell me how to get a replacement.

About the fuel gauge, I was actually looking online this morning at the WEMA fuel senders. Amazon prime has them for ~$50. I held off on buying one because I want to take my old one out and measure the length. My Medaillion gauge always reported full and then when I switch to Faria, it shows half full but my tank is currently full... I never had an accurate reading with the current sender so I will probably switch it out.

Fullpass
03-06-2017, 06:38 PM
The other wire not in use...orange/stripe....secondary speedo cal..switch wire maybe Those swithes will have nothing to calibrate with new speedometer right

outoftheoffice
03-08-2017, 12:16 PM
Thanks a ton for the photos, clvanasch. Also, sorry for any of my previous (and future) dumb questions.

I took a look at my engine block and saw I have the same plug you removed to install your second temp sender. Are you thinking the temperature problem with yours is now the sender? Also, how did you end up running the wire from your new sender to the dash? That seems like it's going to be fun!

It looks like Faria makes their own temp senders (link below); I would sure expect one of these to work with their own gauge. Price on Amazon for these looks around $20, too. Do you happen to know which of these we'd need? I assume the 'American Single Standard' but wasn't sure if 1/8, 1/4, 1/2 or 3/8. I'm kinda thinking it's the 1/2..

http://fariabeede.com/products.php?calledGauge=4_temp

Copy all on the fuel sender. Looks like Faria also sells a sender but I'd probably go with the WEMA over theirs. Output ohms is the same for both (american standard). I know I'll need to swap mine out so hopefully this week I can pull mine and check the length.

Fullpass - not sure I fully understand what you're talking about doing?

outoftheoffice
03-10-2017, 09:07 PM
Got the old stock fuel sender pulled and measured today. I also measured the depth of the tank and it was 10" from the bottom of the tank to the outside of the top of the tank (where the sender mounts. Based on this measurement and the length of the stock sender I ordered the 9" WEMA two wire sender. That should be the correct length but if not I'd rather it be a little short than too long.

http://i297.photobucket.com/albums/mm219/outoftheoffice/3273C5FD-BD52-48AD-A3A9-42EF5E555553.jpg

http://i297.photobucket.com/albums/mm219/outoftheoffice/08373702-6B41-4083-947B-8A31DF94EAD4.jpg

I also tried to pull the plug from the other side of the block but that thing is a beast! I was wrenching on it with a 3/8" Allen wrench with no luck so I'll have to try adding some leverage next time. Did you need to do anything specific to get it out? Maybe warm the engine up?

lakedawg
03-22-2017, 09:49 PM
I paid a little extra and got the Centroid sensor made just for my boat in a 3 wire config so it was plug and play. I can get you more info if interested.

bdiesel
03-23-2017, 08:07 AM
I paid a little extra and got the Centroid sensor made just for my boat in a 3 wire config so it was plug and play. I can get you more info if interested.

Please post the info on the 3 wire sender.

CheeseSteak1
05-02-2017, 12:07 AM
Any updates on 03' witch hunt? I really want to do the delete on my 03'.

jchance
05-03-2017, 10:22 AM
Call Joel at Centroid. He can tell you exactly what you need.

jchance
05-03-2017, 10:24 AM
Swapped mine in a '01 this winter and VERY happy with results. Glad to get rid of the analog to digital box. It didn't provide me with any info that the gauges don't and no grounding issues.

CheeseSteak1
05-05-2017, 12:23 AM
Call Joel at Centroid. He can tell you exactly what you need.

Will do. Thanks

razorback64
05-05-2017, 11:05 PM
Have been following this post for a couple of years - finally fed up with MDC. 2003 X-10
Seems every production year has different configuration and that is what I'm having trouble following.
I have a tach with hour meter that works flawlessly. Also PP with paddle wheel that works well - three paddle wheels in about 6 years. All other gauges are intermittent. I did finally determine that my temp gauge works through the MDC and sender is two wire ecm, so I know I'll need to run new feed from separate sender.
CAN ANYONE TELL ME IF THE PADDLEWHEEL WIRING IS SEPARATE FROM THE MDC or if I'll encounter rewire issues there? I did pick up someone's post about picking the grey tach wire up from the PP.
Thanks to all who have contributed to this project.

jchance
05-07-2017, 02:43 PM
The PerfectPass wiring is separate on mine. The only thing it needs is a tach connection.

outoftheoffice
05-09-2017, 09:16 AM
OK, after some additional work I've got an update from my 2003 X-30. I'll start with the temp sender:

I liked what clvanasch did on the opposite side of the engine block with removing the plug and installing a separate temp sender there, but man, he must have been the hulk to get that done! I tried everything I could with hand tools and couldn't get the plug to budge. I eventually removed the stock sender and put together the setup pictured below in the stock sender location. I'm not happy with it, and am a little worried about the functionality (will the water in the T fitting sit stagnant and not provide a reliable reading?), but I haven't fired up the engine to test it out yet. I'm hoping that if I get a good reading on my gauge that will verify the stock sender should be seeing a good temp, too. I found the single wire, 3/8" thread temp sender on the top of the stack for I think under $30 locally.

http://i297.photobucket.com/albums/mm219/outoftheoffice/14C469C5-3523-4DFC-8F27-4EDEC2973D90.jpg

http://i297.photobucket.com/albums/mm219/outoftheoffice/D50FEC45-5A9B-4A77-B8EE-4251013A5077.jpg

http://i297.photobucket.com/albums/mm219/outoftheoffice/D44A1CEC-01D5-4FE5-8722-6F4FB665858C.jpg



Next was the fuel sender:

I knew I was going to need to swap out the stock 3 wire sender for a 2 wire. I installed the 9" WEMA two wire sender - it dropped right in, install was a breeze. I was hoping I would just need to ground one of the wires then tie the other into one of the three wires on the boat's wiring harness but no matter what combination I did I could never get a resistance reading at the dash wiring that made any sense. Whenever I took a resistance reading directly from the sender I would get around 57 ohms (3/4 to full tank), which corresponded to how much gas was in the tank, so I knew the sender was reading correctly and that was my target resistance reading. After trying a few different things I eventually ran the two wires from the sender all the way up to the gauge - since this config wasn't grounded the gauge gave me a 1/4 tank readout. Once I tied in the wiring harness ground into the gauge I had an accurate readout.

http://i297.photobucket.com/albums/mm219/outoftheoffice/A6A7510B-7866-4DB3-AC4B-C508D8229D2B.jpg



All in all so far I had to run three separate wires from the engine/fuel tank up the dash (the fuel sender could have probably been only one wire), which ended up being much easier than I thought it was going to be. Unfortunately I realized too late that my fuel gauge is faulty so I'm waiting on a new one to arrive. Once I get that installed I'll fire everything up and hopefully provide a final positive update!

I don't claim to be an expert on this work but have been through quite a bit of 'delta' chores associated with the conversion so if anyone has issues with boats of similar year models please feel free to PM me and I'll try to help where I can.

I think I can finally see the light at the end of the tunnel!

outoftheoffice
05-10-2017, 04:53 PM
Have been following this post for a couple of years - finally fed up with MDC. 2003 X-10
Seems every production year has different configuration and that is what I'm having trouble following.
I have a tach with hour meter that works flawlessly. Also PP with paddle wheel that works well - three paddle wheels in about 6 years. All other gauges are intermittent. I did finally determine that my temp gauge works through the MDC and sender is two wire ecm, so I know I'll need to run new feed from separate sender.
CAN ANYONE TELL ME IF THE PADDLEWHEEL WIRING IS SEPARATE FROM THE MDC or if I'll encounter rewire issues there? I did pick up someone's post about picking the grey tach wire up from the PP.
Thanks to all who have contributed to this project.

What's your plan for post-gauge swap? Are you going to stick an analog Tach in there and use PP for speed? If so, that's the same thing I did except my original set-up had a large speedo (instead of a tach) along with the PP.

I believe anything that runs through or is displayed on your PP should still work after the MDC is removed. I say believe because I haven't dropped my boat back in the water yet to test everything out. I do know picking off the correct wire from the PP wiring to feed my analog tach worked (the gauge had a reasonable value when running the engine on a hose). I feel fairly confident, though, because I couldn't imagine PP would need any of the proprietary digitized data that the MDC would be kicking out (only the matching proprietary gauges would use those signals); I would think the PP would only run off standard boat telemetry along with any of their own proprietary stuff.

Good luck with the swap!

jchance
05-11-2017, 01:54 PM
That is correct. The early ones had nothing to do with the MMDC except a shared tach wire. Everything on mine works including an accurate fuel gauge after replacing it with the one from Centroid.

outoftheoffice
05-19-2017, 11:16 AM
FINALLY...I am done with my swap.

I dropped a new fuel gauge in, fired up the engine and everything works! Temp sender came up to operating temp in a normal amount of time and had a readout of around 125 after 5-10 min. I used a temp gun to compare the temps at the brass T fitting I installed vs the black engine block just below it (where the original temp sender was installed). The difference was consistently around 10 degrees F. In the short term I'm not too worried about this and plan to check it again next time we're on the water for a longer period of time. I found up to three other potential spots to tap into that I may consider moving the single wire sender to in the future: port on the block down under the exhaust manifold on the starboard side of the engine (same as knock sensor but opposite side of engine), two ports near the spark plug wires, one on either side of the engine (but my understanding of these ports is that they'll read head temperature, which will consistently be ~10 degrees F hotter than the stock sender location on top of the block).

Good luck to anyone else out there that might go down this path and feel free to PM me if you have any specific questions - I don't mind at least trying to help (even though I might not know the answer!).


Before:

http://i297.photobucket.com/albums/mm219/outoftheoffice/IMG_2738.jpg


During:

http://i297.photobucket.com/albums/mm219/outoftheoffice/IMG_2740.jpg


After:

http://i297.photobucket.com/albums/mm219/outoftheoffice/DBCB08EF-2600-4BE9-865B-D831B2FA1C28.jpg

http://i297.photobucket.com/albums/mm219/outoftheoffice/3CC96989-F701-4B75-8DBD-10C3F665AC5B.jpg

CheeseSteak1
05-24-2017, 07:40 AM
OK, after some additional work I've got an update from my 2003 X-30. I'll start with the temp sender:

I liked what clvanasch did on the opposite side of the engine block with removing the plug and installing a separate temp sender there, but man, he must have been the hulk to get that done! I tried everything I could with hand tools and couldn't get the plug to budge. I eventually removed the stock sender and put together the setup pictured below in the stock sender location. I'm not happy with it, and am a little worried about the functionality (will the water in the T fitting sit stagnant and not provide a reliable reading?), but I haven't fired up the engine to test it out yet. I'm hoping that if I get a good reading on my gauge that will verify the stock sender should be seeing a good temp, too. I found the single wire, 3/8" thread temp sender on the top of the stack for I think under $30 locally.

http://i297.photobucket.com/albums/mm219/outoftheoffice/14C469C5-3523-4DFC-8F27-4EDEC2973D90.jpg

http://i297.photobucket.com/albums/mm219/outoftheoffice/D50FEC45-5A9B-4A77-B8EE-4251013A5077.jpg

http://i297.photobucket.com/albums/mm219/outoftheoffice/D44A1CEC-01D5-4FE5-8722-6F4FB665858C.jpg







Why couldn't he just replace the old medallion specific sending unit with a standard single pole vs going with the tee fitting route? This project was on the shelf till the next off season but I can't take it anymore. Oil pressure started acting up this past week. I'm getting normal readings, needle pegged, no reading at all, etc etc.... I can deal with no fuel readings. Is it a pain in the @$$ sometimes? Absolutely! Oil pressure is a whole different kind of mind game. It's time for a MCD-lobotomy! Gauges are ordered, Wema fuel sender is delivered and I still need to pick up a temp sender. Anyone know what size? 1/2"? I would like to remove the old one completely but don't know if this will cause issues.

My Questions
Is the tee fitting with both new and old sender necessary or can I just replace the old with the new?
Temp sender size?
Am I missing anything?

Thank you

outoftheoffice
05-24-2017, 11:21 AM
Why couldn't he just replace the old medallion specific sending unit with a standard single pole vs going with the tee fitting route? This project was on the shelf till the next off season but I can't take it anymore. Oil pressure started acting up this past week. I'm getting normal readings, needle pegged, no reading at all, etc etc.... I can deal with no fuel readings. Is it a pain in the @$$ sometimes? Absolutely! Oil pressure is a whole different kind of mind game. It's time for a MCD-lobotomy! Gauges are ordered, Wema fuel sender is delivered and I still need to pick up a temp sender. Anyone know what size? 1/2"? I would like to remove the old one completely but don't know if this will cause issues.

My Questions
Is the tee fitting with both new and old sender necessary or can I just replace the old with the new?
Temp sender size?
Am I missing anything?

Thank you

I think we already talked your first question in the other thread but I really hope someone else chimes in here to help confirm or deny my understanding. If you do add the second sender maybe you'll have better luck getting the plug on the opposite side of the block out and install the sender there, like what clvanasch did? That would have been my first choice and the best place to get a similar reading to what the stock sender sees (I just couldn't get that plug out on mine).

I really might end up putting the second, single wire sender in the port on the side of the block, although I'm worried about it reading higher than the stock sender due to it reading the head temp at that location. Also, I'm not sure what the thread size is at that location but I know it requires some non-standard size of square drive tool to remove it (it's between 1/4" and 3/8", I think some size common to engine building). If you do the tee or replace the two wire sender with the single one then you'll need a 3/8" sender. Maybe you have more courage than me and could install the single wire sender and try hooking it up to the factory harness and fire it up to see what it does? I'd be very interested to see what those results are (both how the engine runs and what the gauge reads).

Sorry to hear your system is going south. I was in the same exact place as you - my fuel gauge never really worked, which was annoying, but when my oil pressure gauge starting acting up (was failing just like yours) I immediately put a tee fitting and a manual pressure gauge at the oil pressure sender port which confirmed the gauge was wrong and the engine was still operating nominally. But I agree, I could not deal with a gauge that important not working right.

Good luck!
Please let us know how it goes!

DanMahx
05-24-2017, 11:49 AM
I just went through this process on my 03 Maristar 210. For the temp sensor I removed the plug on the right bank head. I took off the cooling hose, popped off the throttle cable, and removed the throttle body - just three nuts and real easy. That gives you plenty of room to get a 3/8" hex socket with a breaker bar on the plug (I used an impact wrench). I think it's important to have the sensor in the water flow to get an accurate reading. The plug/sending unit is a 1/2" thread. I ran a 14GA wire from the sender to the gauge. Running it along the starboard gunwale with the big ground and power cables was pretty easy. No need to take the whole boat apart. You can't remove the two wire sending unit because it talks to the computer for engine management.
A few other tips:
- I removed my steering wheel/tilt/rack assembly, radio, and the entire console. This was easier on my boat because the instrument panel had hex nuts instead of wing nuts. It also gave me plenty of access to clean up the harnesses. And I've changed so many inboard steering cables that it was no big deal.
- I ran a 14 GA ground wire from the instrument harness (close to where it splits to go to the instruments) directly to the ground buss behind the console. Less that 2 feet of wire. The 20 GA wire from the MMDC harness is inadequate and things were a little strange until I ran the new ground. You really need a good heavy ground with the new analogue gauges. In hindsight I should have tried running the new ground on the input side of the MMDC before I did the conversion - it may have fixed the problems.

- The MDC wiring is a little different from the MMDC, so be aware of that. For instance, no tach (grey) wire. The tach wire can be found in the PP harness behind the kick panel under the console where the harnesses disappear into the floor.

Good luck.

CheeseSteak1
05-24-2017, 12:20 PM
I think we already talked your first question in the other thread but I really hope someone else chimes in here to help confirm or deny my understanding. If you do add the second sender maybe you'll have better luck getting the plug on the opposite side of the block out and install the sender there, like what clvanasch did? That would have been my first choice and the best place to get a similar reading to what the stock sender sees (I just couldn't get that plug out on mine).

I really might end up putting the second, single wire sender in the port on the side of the block, although I'm worried about it reading higher than the stock sender due to it reading the head temp at that location. Also, I'm not sure what the thread size is at that location but I know it requires some non-standard size of square drive tool to remove it (it's between 1/4" and 3/8", I think some size common to engine building). If you do the tee or replace the two wire sender with the single one then you'll need a 3/8" sender. Maybe you have more courage than me and could install the single wire sender and try hooking it up to the factory harness and fire it up to see what it does? I'd be very interested to see what those results are (both how the engine runs and what the gauge reads).

Sorry to hear your system is going south. I was in the same exact place as you - my fuel gauge never really worked, which was annoying, but when my oil pressure gauge starting acting up (was failing just like yours) I immediately put a tee fitting and a manual pressure gauge at the oil pressure sender port which confirmed the gauge was wrong and the engine was still operating nominally. But I agree, I could not deal with a gauge that important not working right.

Good luck!
Please let us know how it goes!

Sorry bud, I missed your response on the other thread. This makes sense and I figured there was a reason. Thank you

CheeseSteak1
05-24-2017, 02:08 PM
I just went through this process on my 03 Maristar 210. For the temp sensor I removed the plug on the right bank head. I took off the cooling hose, popped off the throttle cable, and removed the throttle body - just three nuts and real easy. That gives you plenty of room to get a 3/8" hex socket with a breaker bar on the plug (I used an impact wrench). I think it's important to have the sensor in the water flow to get an accurate reading. The plug/sending unit is a 1/2" thread. I ran a 14GA wire from the sender to the gauge. Running it along the starboard gunwale with the big ground and power cables was pretty easy. No need to take the whole boat apart. You can't remove the two wire sending unit because it talks to the computer for engine management.
A few other tips:
- I removed my steering wheel/tilt/rack assembly, radio, and the entire console. This was easier on my boat because the instrument panel had hex nuts instead of wing nuts. It also gave me plenty of access to clean up the harnesses. And I've changed so many inboard steering cables that it was no big deal.
- I ran a 14 GA ground wire from the instrument harness (close to where it splits to go to the instruments) directly to the ground buss behind the console. Less that 2 feet of wire. The 20 GA wire from the MMDC harness is inadequate and things were a little strange until I ran the new ground. You really need a good heavy ground with the new analogue gauges. In hindsight I should have tried running the new ground on the input side of the MMDC before I did the conversion - it may have fixed the problems.

- The MDC wiring is a little different from the MMDC, so be aware of that. For instance, no tach (grey) wire. The tach wire can be found in the PP harness behind the kick panel under the console where the harnesses disappear into the floor.

Good luck.

Thank you for the input! Very helpful. Love using my 24" breaker bar. No need for heat?

outoftheoffice
06-06-2017, 11:31 AM
Update on my temp sender setup:

I had the boat out a couple days and took temp gun readings at various points during the day both on the brass T fitting and the black painted portion of the engine block just below it. The temp gauge showed the engine was running at about 150 deg all day. The temp gun on the brass T fitting showed about 5 degrees cooler than the gauge temp. The temp gun on the black painted portion of the engine block showed 10 deg warmer than the gauge temp. So, to me, the temps are looking close enough to feel comfortable with this setup at least for a little while. Is it the best set-up? No. But it will at least work. I agree with DanMahx and would prefer both senders to be in the water flow path and can hopefully follow his steps to remove the plug on the other side of the engine and drop a new sender there next chance I get.

http://i297.photobucket.com/albums/mm219/outoftheoffice/D44A1CEC-01D5-4FE5-8722-6F4FB665858C.jpg