PDA

View Full Version : High altitude, slow boat, Help


Goinbroke
06-18-2007, 12:52 PM
Ski lake at 6000' losing 18% in HP/TQ due to high altitude. I've tried 4 different props but still run at about a 37-38MPH top speed and not real stong out of the hole.
The Boat:
2004 SD ProStar 197 / MCX 350.

What about a heads and Cam option? has any one had any experience with engine mods on these motors?

thanks in advance.

:cool:

CoFooter
06-18-2007, 06:54 PM
Put on a supercharger. Guy out here is doing that - we'll have to see how it works out. Maybe a little extreme. Your top end is not surprising. Problem is changing prop pitch dials your RPM in and the engine becomes more efficient/less strain, but you loose forward motion due to the lower pitch. Simple math. I don't think heads and/or cam are going to come anywhere close to 18% which is about right. I have the same problem at 5,000 ft. Thats why most of my time is spent behind an outboard where we can trim it out.

Goinbroke
06-18-2007, 07:05 PM
CoFooter, thanks for the reply. I would be very interested to see how Blower works. Please keep me posted. I really dont need to make up the full 18% or 60HP, I would just like to get a little more grunt out of it. I can tow a skier at 36mph but thats at full throttle.
What prop do you run??

CoFooter
06-18-2007, 07:30 PM
I run a 3 bld 13x11.5 on a 375HP motor and a 3 bld 13x10.5 on a 330 HP motor. Really depends on your boat and motor. Choose a prop that gets you to the rated RPM's (without exceeding) at wide open throttle (WOT) position. Most engines need upwards of the full WOT RPM's to generate their horsepower ratings. What is your motor and what RPM's are you running vs what your WOT RPM rating is? You already may know all of this so forgive me if this is elementary.

I'll check on the supercharger thing and let you know.

Storm861triple
06-18-2007, 09:19 PM
You could make up the 18% diff w/a cam head package, such as AFR 195's and a good roller cam in the 230 duration range....but low end torque and idle would suffer, and I don't know how you'd get a marine ECM tuned for that much change.

To get "back" the power that you had at low elevation WITH the character that you're used to, you've got two options;
*Forced induction -as mentioned above
*More displacement I.e. a Small block 400 w/your heads, stock cam and intake would make around 400 hp at sea level. Minus 18% is over 312 hp.

rstitson
06-18-2007, 11:19 PM
Run high test. One thing I noticed while driving through the high plains in my vette is that the octane rating goes down considerably for the grades. Might be silly but .... I am at sea 100 ft above see level and just got 47 miles/hour on an x-15 (heavier boat) with a MCX pushing 5000 rpm with more available.

Storm861triple
06-19-2007, 12:15 PM
That's because at high elevation you don't need as high an octane rating. As atmosphere decreases, cylinder pressure decreases a proportionate amount..which is why power drops. Since you have lower cylinder pressure, (similar to having a lower compression ratio), you don't need as high and octane rating to avoid detonation. Increasing octane won't gain you anything measurable or worth while.

You need CUBES or CHARGERS.

EJ OJPROP
06-19-2007, 12:31 PM
What size propellers have you tried? What is the max RPM those props would turn?

Ric
06-19-2007, 12:44 PM
Ski lake at 6000' losing 18% in HP/TQ due to high altitude. I've tried 4 different props but still run at about a 37-38MPH top speed and not real stong out of the hole.
The Boat:
2004 SD ProStar 197 / MCX 350.

What about a heads and Cam option? has any one had any experience with engine mods on these motors?

thanks in advance.

:cool: welcome. LOVE the screen name!

Goinbroke
06-19-2007, 06:35 PM
Ok, I have done some home work.
Arizona Speed and Marine will re-program the DELPHI MEFI for $400.00 The also sell the software (Ingenius Marine Software) to tune your motor yourself. I am doing both. I'm sending my MEFI to them to be re-flashed. Kelly at ASM told me the stock programing is pig rich and that I might see as much as 20HP! I have enough experiance with automotive software I'm looking forward to being able to plug the old laptop in an see whats happening real-time.
I will keep you all posted on the results.
Might have the boat back on the water by Friday.

Goinbroke
06-19-2007, 06:38 PM
EJ, I have a 12.5 X 12 on right now and I can tell you exactly what the max RPM is. I will check in the am. Finally the weather is co-operating for the 7am before work ski.

Goinbroke
06-21-2007, 01:11 PM
Oj, my 12.5X12V is slightly damaged, I'm sending it to you for repair. I think it will help quite a bit.

Willski
06-21-2007, 08:50 PM
How do you know your loss rate? Not doubting, just curious. Did you somehow dyno it?

NeilM
06-22-2007, 11:00 AM
How do you know your loss rate? Not doubting, just curious. Did you somehow dyno it?

Willski: a rough rule of thumb for normally aspirated engines is 3% loss in HP per thousand feet of altitude, therefore 6000 feet = 18% using that rule of thumb. In actuality, it's not that linear of a relationship between altitude and HP, but it's close enough..

JimN
06-22-2007, 11:32 AM
Goinbroke- what year is your boat?

Goinbroke
06-22-2007, 12:57 PM
04 SD Pro-Star 197 with a MCX 350.

JimN
06-22-2007, 04:03 PM
Is it still under warranty or does that not matter? I know it's almost out but if it's recalibrated with something other than the MC program, it won't be under warranty after. Yeah, yeah, the place in AZ does it all the time but it's still not a factory change, which begs the question, have you called MC to ask what they have for high altitude calibrations? I know they have some and they have done a lot of testing up in that range.

Goinbroke
06-22-2007, 04:16 PM
Great coment Jim.
I will call my dealer. I have asked them about high altitude perf before, but not the specific question of a re-flash.
I will let you know if I find out MC has a high altitude program.
thanks a ton.

Goinbroke
06-30-2007, 10:15 PM
Just got my MEFI back for AZ Speed and Marine.
Plugged it in and TEMP light came on and it wont start!

Not Happy

:(

Thrall
07-03-2007, 03:41 PM
Just got my MEFI back for AZ Speed and Marine.
Plugged it in and TEMP light came on and it wont start!

Not Happy

:(

Refer to Jim N's previous post! j/k man, sorry to hear about it.

Thrall
07-03-2007, 05:41 PM
rstitson, As Tom explained, it's not the high octane fuel that's doing it for you (with everything else the same). What combo do you have trans ratio and prop on your X? That may help Goinbroke.
I don't know what prop is spec'd for your boat, but the 12.5" dia may be small. Most every 1:1 ski/wake boat runs a 13x ..... prop.
My boat, similar size,config to yours, is a bit of a slug at 6k ft lakes. It only runs up to about 4400rpms, s/b 5000 rpms. At 4kft, I get about 4600 rpms out of the stock OJ 13x13. Top speed seems to be over 36mph, but I don't have a GPS and can't ski that fast w/o killing myself!
I'm putting an Acme 543 (13 x 11.5) on my boat tonight and will be running at 4kft elev tomorrow. Will post the difference.
Also, keep us up to date on the ECM recal, thru AZ marine or MC. Wondering how that will work out power wise. My LT1 w/ a MEFI II controller seems to compensate very well for altitude. Have never noticed it running rich. Plugs look clean, no exhaust smoke at all. I can tell the power loss at altitude when driving, but can't feel any difference from the rope end when getting pulled up, even at 6kft.

EJ OJPROP
07-03-2007, 05:50 PM
Thrall - The 13 X 13 LC 4-blade you have is really less than 13" in diameter. The CNC machined 12.5 X 12 is a replacement for the 13 X 13. I would suggest our 13 X 11 for your elevation.

Thrall
07-03-2007, 06:23 PM
My mistake Eric. I didn't realize that. Also, I have the 13x13 OJ 3 blade (original on the boat) currently and have now purchased a 13x11.5 Acme (I know, shoulda tried your prop as well) for my operating elevation.
I appreciate your advice, though. Thanks

ride
08-09-2007, 07:57 PM
Just got my MEFI back for AZ Speed and Marine.
Plugged it in and TEMP light came on and it wont start!

Not Happy

:(
Goinbroke-
You ever get your MEFI resolved? Did it add ponies? Had a similiar issue on my '95 that Indmar couldn't dial in exactly, thus I'd love a way to lean mine up for altitude just a bit.

Storm861triple
08-09-2007, 08:21 PM
Goinbroke-
You ever get your MEFI resolved? Did it add ponies? Had a similiar issue on my '95 that Indmar couldn't dial in exactly, thus I'd love a way to lean mine up for altitude just a bit.
If you're rich across the board, ONE WAY you can improve the situation (for free) is to simply lower your fuel pressure a pound or two at a time, then read plugs, until you get it optimized.

ride
08-09-2007, 08:31 PM
If you're rich across the board, ONE WAY you can improve the situation (for free) is to simply lower your fuel pressure a pound or two at a time, then read plugs, until you get it optimized.
Storm861triple
Is that advised on the LT1's high pressure system? How does one lower their fuel line pressure with that recirculating pump? I'd love an easy solution, if it exists.

JimN
08-09-2007, 09:23 PM
Actually, the easiest way to reduce the fuel delivered is to decrease the pulse width. Have the dealer call Technical Services to see if they have a high altitude calibration. I know they have done testing up in the mountains and they should have something they can e-mail to the dealer so they can reprogram it. It's less likely that the dealer has done the testing and has the software for making discreet changes to the LT-1 calibration.

ride
08-09-2007, 10:42 PM
Actually, the easiest way to reduce the fuel delivered is to decrease the pulse width. Have the dealer call Technical Services to see if they have a high altitude calibration. I know they have done testing up in the mountains and they should have something they can e-mail to the dealer so they can reprogram it. It's less likely that the dealer has done the testing and has the software for making discreet changes to the LT-1 calibration.
JimN-
I'm new to the forum (actually am a return member from the old site days) and it seems you're one of the best and brightest from what I've read. Thanks for the tip. Is it very recent that the dealer has the ability to reprogram ECM's at their shop? It was my dealer that sent mine to Indmar for recalibration (this was 4 or 5 years ago).

JimN
08-09-2007, 10:57 PM
Recent? No. I stopped working on these in March of '01 and we had been doing the recals the year before. If they don't keep their techs well trained or don't have a laptop, it's harder but still possible. Some aren't real tech-oriented, as far as computers, etc. It's not hard to do but some people don't want to deal with it. Personally, I think it's just good Customer Service to keep them on the water as much as possible, especially when they have an expensive boat.

For the small amount of time a recal takes and the fact that it's actually easy, it makes no sense to me that dealers don't do them, unless Indmar and MC stopped authorizing them. Out of warranty, they have less liability but could still supply the programs.

Maybe one of the dealers can fill in whatever blanks I left.

Storm861triple
08-09-2007, 10:59 PM
Actually, the easiest way to reduce the fuel delivered is to decrease the pulse width.
Only if you have money or connections. If you have neither, then FP is the cheapest and most obtainable way. Which is why I posted my low-budget, but effective method.

I agree w/Jim that the dealer should WANT to make your boat run the best that it can.

JimN
08-09-2007, 11:01 PM
What connections are needed? The ECM gets sent to Indmar or MC for a recal and is returned to the customer. How much easier can it be?

Storm861triple
08-09-2007, 11:07 PM
I guess that I'm not sure. I'm ASSuming that if it's out of warranty, then you ned to pay for the labor of DL'ing a new program. No?

If yes, and you have no money then the next best thing would be to have a "connection" such a s friend that's also a dealer etc.

JimN
08-09-2007, 11:12 PM
I just ASSume that people who own boats, make sure they have at least one connection at a boat dealer. Best thing to do is call a dealer (or more than one) and find out what they need to get for this kind of work. Doing it during the boating season makes it possible to make sure it works, but as I said, it doesn't take a long time to recal an ECM.

Storm861triple
08-09-2007, 11:34 PM
I just ASSume that people who own boats, make sure they have at least one connection at a boat dealer.
That's a good assumtion, I'd say. I didn't think of that because:
1. Our dealer (Utah Water Sports) sucks up one side and down the other
2. I can fix my own boat better than they can
3. I can't afford to pay someone to fix my boat so I do it myself anyway; I HAVE a boat BECAUSE I save money by doing things myself.

Since the OP asked I posted the most economical and easy way I know. If one has the means (what ever that is) then surely a dealer DL'ing a program is easier than doing manual labor oneself, and obviously more correct. But, it's not the only option.

ride
08-09-2007, 11:39 PM
I just ASSume that people who own boats, make sure they have at least one connection at a boat dealer. Best thing to do is call a dealer (or more than one) and find out what they need to get for this kind of work. Doing it during the boating season makes it possible to make sure it works, but as I said, it doesn't take a long time to recal an ECM.
I'll try anything if it works. I'm thinking that my dealer's sick of me on this tho, as I had them send it back and forth to Indmar like 3+ times and its still not dialed. Letting the dealer off the hook a little tho, Indmar informed me that the '95 ECM wasn't as reprogramable as say the '93 & '94 versions. JimN, had you heard anything along that line hile you were turning a wrench on them?

Leroy
08-09-2007, 11:39 PM
Goinbroke;
I'm surprised 18% lower HP would cause this and why isn't everyone in CO complaining? Have you check the speed with GPS? Do you have the repaired prop back?

JimN
08-09-2007, 11:40 PM
I can see you point but I would be more comfy recommending a way to alter the fuel delivery if it was a different motor. Better to be running rich than lean on an LT-1, IMO.

JimN
08-09-2007, 11:49 PM
The fact that it went to Indmar and not Technical Services is one reason I would have the dealer call them, so they can get to know who did the actual testing. MC has the testing done specifically for their boats, not just a boat. Alan and the others went to the mountains so they could gather data and they're the ones I would have the dealer talk to. Dealers west of the Rockies may not know of him much because they usually go to Corona, CA for training, which is less MC specific, unless Alan runs the classes there, too.

The controller in '95 may be less adjustable, but they should be able to change the fuel mapping. It's just pulse width and computers are good at counting, if nothing else. I didn't get into EFI until early '98, but we still discussed the earlier ECM units and I don't remember hearing that the ones from '95 were harder to recal.

Have your dealer call Technical Services. If they don't know who they are or how to contact them, they need to call MC and talk to the technical department. TS is in Indiana.

ride
08-10-2007, 12:21 AM
The fact that it went to Indmar and not Technical Services is one reason I would have the dealer call them...
Alan is in Indiana right? Really nice guy, he was my contact the multiple times I tried to get it recalibrated. He also told me about the '95 ECM being so finicky. As I recall, I ended up sending my buddies '93 ECM in along with mine to try to match check sums. We got mine close, but if I swap my buddies ECM, it runs like a raped ape. I'd give my left nut for mine to run that well all the time.

JimN
08-10-2007, 05:47 AM
You two have the same model of boat? How does his boat perform with your ECM?

Did you tell Alan how yours runs with your friend's ECM after they came back? (I assume you did, which was the reason for sending both)

ride
08-10-2007, 07:56 PM
Yes, same model and engine (different year). That's a good question about his boat with my ECM. I don't think it dawned on me to try mine in his since his already ran so well. Its been a while, but do recall telling Alan about it, as it was his idea to send him both mine and my buddies ECM back so that he could try to match them. He could only sum up the final difference in performance by saying that the '93 ECM was more "moldable/reprogramable" than my '95. Do you know if MC used the same ECM part no. on their LT1 AND on their TBI in '93? (Or was it '94 that MC put out the TBI as a production engine?) I figure my only shot at getting this thing perfect at this point is swapping my ECM out for one from a '93 and recal'ing it to my buddies program. However, as you know, that'll be tough to do if MC only put that ECM on their LT1 in '93.

JimN
08-10-2007, 09:01 PM
I don't know if you'll be calling Alan on this but at some point (and I'll have to look in my notes for the time frame), one of the differences in the ECM and wiring was to change from positive output for relay triggers to negative. This means that if one harness is different form the other, it shouldn't work. If you can run your boat on his ECM, I think that point is moot.

Swapping it with a '93 ECM- good luck finding one. I would ask Alan about this. Who knows? He may have one. He would also know if they used the same part for TBI and LT-1 in that year. AFAIK, the TBI was introduced in '94.

ride
08-10-2007, 09:09 PM
So, doesn't that mean I've got a 1 in 100 shot at finding one?? Yea, i'll need whatever luck I can get.

JimN
08-10-2007, 09:21 PM
Look on the back of yours and his ECM for a part number, then google it and look on ebay.

Storm861triple
09-07-2007, 06:04 PM
Hey Ryan,

I've been back from Maine for a few days now and I've tried to email you back a couple times, but I keep getting "Failed Mail". Any idea what's going on?

-Tom

ride
09-15-2007, 02:01 PM
Hey Ryan,

I've been back from Maine for a few days now and I've tried to email you back a couple times, but I keep getting "Failed Mail". Any idea what's going on?

-Tom
Sorry Tom. Email issue is resolved. Heading to the lake tomorrow for a week and plan to make adjustments to a couple of things and see what shakes loose. I'll post my findings when I return... I'd love to come back with an easy cure to altitude sickness in the modern EFI engine:cool:

JimN
09-15-2007, 04:45 PM
"I'd love to come back with an easy cure to altitude sickness in the modern EFI engine":

A motor needs three things to run- spark (at the right time and intensity), compression and the right fuel/air mixture. Make sure all three are correct and it should run as designed.

Have you, or can you, run it closer to sea level? The only thing high altitude does is make it run rich, due to less air molecules being fed to the cylinders.

ride
09-15-2007, 05:05 PM
Hey Jim. Its that specific mix that I want to get correct. I've checked both high alt. and sea level and (although sea level is much better), I beleive I'm still a little rich across the board. Again, we're all in agreement that its likley my pulse width.

JimN
09-15-2007, 05:17 PM
"I'd love to come back with an easy cure to altitude sickness in the modern EFI engine"

Have you talked to Alan about this recently? I know he and his guys have been out there for high altitude testing.

Unfortunately, with thin air, there's only so much that can be done.

ride
09-15-2007, 05:28 PM
I haven't called Alan T. yet, but its on my to do list. I'm heading on this trip and will play with it. At very least, hopefully it'll provide me with a more specific evaluation of issues for the call, once I return.

Storm861triple
09-17-2007, 12:48 AM
Glad you got the email sorted out! I hope youre trip is a success, and I'm looking forward to the results of your data gathering when you return. Keep us updated! :)

-Tom

Storm861triple
09-26-2007, 05:27 PM
So give us the scoop! How did the trip/tuning go? Any progress?

ride
09-26-2007, 06:45 PM
Yup, I'm back, but I've been delaying my findings (for good reason and will get to that in a min.) So while on the lake for a week, I ended up splitting my time on the MC between playing on the water and yanking my engine cover off and gathering data. First item I played with was three different props (EJ, your 13X11 CNC is the shiznit for my boat at altitude!) I tried all three and noted the pros/cons of each on that lake. I then made some very slight fuel pressure adjustments via an adjustable fuel pressure regulator and analyzed my changes with a FP gauge and A LOT of spark plug observations. I can give the long version in a new post if anyone's interested, but the short version is by lowering my FP by between 3 and 4 psi I saw notable increases in throttle response in all positions from holeshot thru top end while at 4000' elevation. I was stoked that a turn of a wrench could give me even a little response, but my non-dyno estimate is at least 10-20 more horses. I was amazed and am a little embarrased for not looking into that before now. But I'm a bit hesitant to rejoice quite yet as I really want to try it out at 7000' and see how she does. The fear of detonation is ever present in the back of my mind...

As for my delayed post, the real reason I've been laying low is I just got out of surgery this morning that was needed on my thumb. While ski-testing my FP modifications in conjunction with Eric's 13X11 CNC, I think the added umpf in my holeshot was more that one of the ligaments in my right thumb was accustomed to. It could also have been the result from the simultaneous Straightline handle breaking in two, but I like to think that it was from the new ponies that my engine had just realized it had. Regardless, I'm now thinking a bit more seriously about investing in a recoil tube for my pylon.
But hey... a 1/2 hour thumb proceedure in return for that much more throttle response? I'll take that trade-off all day long...

Storm861triple
09-26-2007, 07:35 PM
but the short version is by lowering my FP by between 3 and 4 psi I saw notable increases in throttle response in all positions from holeshot thru top end while at 4000' elevation. I was stoked that a turn of a wrench could give me even a little response, but my non-dyno estimate is at least 10-20 more horses.
YEAH!!! H3LL YEAH!!! That makes me happy. Not only that you created and witnessed your own success, but that it was nearly free!! Nice. :)

I'm a bit hesitant to rejoice quite yet as I really want to try it out at 7000' and see how she does. The fear of detonation is ever present in the back of my mind...
Keep in mind that the chance of detonation goes DOWN, as you go up in elevation, since atmospheric pressure is lower, so is cylinder pressure.

As for my delayed post, the real reason I've been laying low is I just got out of surgery this morning on my thumb. While ski-testing my FP modifications in conjunction with Eric's 13X11 CNC, I think the added umpf in my holeshot was more that one of the ligaments in my right thumb was accustomed to. It could also have been the result from the simultaneous Straightline handle breaking in two, but I like to think that it was from the new ponies that my engine had just realized it had.
Well that's a bummer, but if my boat pulled so hard that it "hurt me", I'd be happy that it had more power than I need. To me, that's "just enough". :) :) :)

ride
09-26-2007, 07:47 PM
YEAH!!! H3LL YEAH!!!
Word! Thanks for the tips and direction.

mrprostar
12-19-2007, 05:59 PM
I have a 96 205 with a very similar problem. Can I do the same corrections with the TBI fuel injection? Its a completely different fuel system, so I doubt it. What else can I do besides a prop change?

Storm861triple
12-19-2007, 06:58 PM
Yes! You can. The FPR is the same design, and can be adjusted in the same manor. In fact, the first engine I learned this on WAS a TBI fed engine.

As for what you can do besides prop change, you can advance your ignition timing some, but that and fuel pressure are both basic tunning measures, where you simply "feed it what it wants". Asside from those, you can do anything that has already been talked about in this thread: heads, cam, supercharger, 1.6 ratio rockers... Any thing that will improve power on ANY small block Chevy, will work on your motor. Just keep in mind that you're looking to increase torque in your current RPM range, not move the RPM range up.

-Tom

mrprostar
12-19-2007, 07:19 PM
Thats great news! The only problem I have is that I have to wait until at least April to test and enjoy changes. I guess I'll have to wait. Thanks, Tom.

Storm861triple
12-19-2007, 07:31 PM
Indeed. I would address this just like a snowmobile, or any other carb'ed engine. Runt it WOT for at LEAST 1 minute, then cut it off clean, and pull and read plugs. Then adjust your FP based on what your plugs tell you. A bit arduous, but not technically hard.

-Tom

mrprostar
02-06-2008, 06:56 PM
I'm looking into fuel pressure regulators for this coming high elevation season. What is the normal fuel pressure for the TBI? There are many different ones at many different prices. Since it is EFI I assume it is higher than my 350 with the carb. Its such a simple device. Is $90 what I should expect to spend?

Storm861triple
02-06-2008, 08:25 PM
Make your stock one adjustable (if it isn't already), and save yourself the money. Most factory FPR's are already adjustable, people either don't know it, or they're welded so you cant access the adjusting screw. If it is welded, you simply grind off the weld blob, and voila'! A free adjustable FPR.

Fuel pressure on your engine should be around 18 OR 30 PSI for TBI, depending on the year.

Lastly, the last time I bought a marine TBI FPR, it was $45 from my local Chevy dealer.

mrprostar
02-07-2008, 11:02 AM
Very good news. Can you possibly send me a picture of where the FPR is on the pump? I wouldn't want to grind in the wrong area.

Storm861triple
02-07-2008, 02:16 PM
The FPR isn't on the pump; it's on the Throttle body assy. If you take off the flame arrestor, you'll see the two injectors mounted above the throttle bores in a housing known as the "injector pod". The top half of the injector pod is fixed to the lower half with I believe 7 torx screws. When you remove those, the injector pod top comes off w/the FPR attached to the bottom side of it. The FPR is held to the injector pod top with 4 torx screws, but only needs to be removed for modification.

For adjustment, you really only need to remove the injector pod top and flip it over to access the screw hole in the bottom of the FPR.

-Tom

mrprostar
02-07-2008, 02:18 PM
Sounds easy enough. Thanks.

denverd1
02-07-2008, 03:32 PM
Nice! i had a feeling you could tune it to get where you're goin. thats cool on the real-time software.

mrprostar
04-01-2011, 11:48 AM
I'm finally getting around to doing this. Having babies is expensive and sooo time consuming! We finally have a chance to get out and use the boat a lot this summer and I have time to get everything running right. Last season I found the timing was way off and it improved performance significantly. Also got a new CNC prop 13 x 10.5 for high altitude. I'm still only getting 4100 RPM max so something else has to going on. Our favorite lake is at 7000 feet so I want to do the fuel pressure adjustments explained above. We are also making a Memorial weekend trip to powell and thats at 3000 feet (I believe) so I don't want to make a drastic change and make it too lean. I'm going to have to adjust and test and adjust. How much should I turn the fuel pressure adjustment? 1/2 turn and test? full turn? Clockwise raises the fuel pressure and counter clockwise lowers, correct? How do you test the fuel pressure because it is regulated right at the injectors?

Oh and the boat is a 1996 205 with the TBI, obviously.

JimN
04-02-2011, 01:47 AM
I'm finally getting around to doing this. Having babies is expensive and sooo time consuming! We finally have a chance to get out and use the boat a lot this summer and I have time to get everything running right. Last season I found the timing was way off and it improved performance significantly. Also got a new CNC prop 13 x 10.5 for high altitude. I'm still only getting 4100 RPM max so something else has to going on. Our favorite lake is at 7000 feet so I want to do the fuel pressure adjustments explained above. We are also making a Memorial weekend trip to powell and thats at 3000 feet (I believe) so I don't want to make a drastic change and make it too lean. I'm going to have to adjust and test and adjust. How much should I turn the fuel pressure adjustment? 1/2 turn and test? full turn? Clockwise raises the fuel pressure and counter clockwise lowers, correct? How do you test the fuel pressure because it is regulated right at the injectors?

Oh and the boat is a 1996 205 with the TBI, obviously.

The fuel pressure isn't controlled at the injectors, it's controlled by the ECM. Injector pulse width is what controls the amount of fuel delivered. If you adjust it at the regulator, you'll screw up the fuel mapping when you go to normal elevations.