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PeteS
09-07-2004, 09:18 AM
Temp gauge is not working. It actually jumps up to around 130 when I fire the boat up, and then drops to 100 when it's operating. Seems odd. I've heard the operating temp should be 150 or so, so I'm assuming this 100 reading is false.

Anything jump out at anyone is quick fixes? Pulled the dash, and the wiring seems to be in tact all the way back to the thermostat. What next?

Thanks,
Pete

JimN
09-07-2004, 09:45 AM
Next, check the wire to the temp sender. Sounds loose if it changes, or the wire has a break in it near the terminal. Could still be a bad sender, but the wiring should be checked before replacing anything.

PeteS
09-07-2004, 10:09 AM
As always, Jim, you are a lifesaver. The sender, is that the unit located in the thermostat hole on the top of the block, drivers side? The wiring looked good coming from there, if I was checking the right place. Thanks again.

JimN
09-07-2004, 10:39 AM
That should be it. It's about the same size(but not as long) as a spark plug with a tan or tan/black wire on it. Turn the key on and see if wiggling the wire changes anything.

PeteS
09-07-2004, 10:43 AM
Great, we are on the same page. I tried wigglingt he wire with the ignition on, and didn't see any changes in the needle on the gauge. Possible bad sending unit?

Like I said, the gauge jumps to 130 during start up and then slowly falls down to around 100 after a few minutes. Thanks again.

PeteS
09-07-2004, 10:46 AM
If this is the right piece, looks like it's only $9.00 at DIM:

http://skidim.com/prodinfo.asp?number=R020003&variation=&aitem=4&mitem=6

acurtis_ttu
09-07-2004, 04:08 PM
Just replace the sending unit. It is very cheap to replace, and only takes a few minutes. Make sure you don't over torque.

PeteS
09-07-2004, 04:13 PM
Thanks for the advice. Does the above sending unit look like the right part?

Hoff1
09-08-2004, 08:25 AM
Donít know how long you have had your boat, but mine had similar issues when I purchased it. I tried replacing the gage a couple of times, with no luck. I pulled the sending unit out, and tested it with a hair dryer. Thing worked without any issues. I was a little confused until I went to replace the thermostat. Found that the previous jacka$$, I mean owner, had removed the thermostat completely. Just a thought.

PeteS
09-08-2004, 08:31 AM
Now that's a classic move, Hoff. Sorry to hear that, it makes me cringe to think that my boat actually may be running at 100 degrees.

I'll try the hair dryer trick. Just pull the sending unit, aim the hair dryer at the bottom, heat it up, and watch the temp gauge with the key on? How long do I have with the key on and the boat not running before I fry my electronic ignition?

Last question, and I know, I know, it's a dumb one. Where are both thermostats located to make sure my previous owner didn't do the same thing yours did? Thanks a million.

JimN
09-08-2004, 08:35 AM
If you don't want to fry the ignition system, disconnect it before starting this. Then, you have all the time you want. It would still be better to use water. Start with cold water in a pan, then add hot water(you can boil water, right?) and watch for the temperature to increase gradually. Verify the temp changes with a thermometer.

PeteS
09-08-2004, 09:25 AM
Thanks for the tip, Jim. I did some searches, and it appears that some people have had thermostats stay open and the boat run low. Could it be possible that my thermostat is stuck open?

Should I go ahead and replace it/them, just to be safe if I don't know if they've ever been changed before? I can still check the sending unit, but if the boat is really running around 100 degrees, how bad of a thing is that? Thanks again.

H20skeefreek
09-08-2004, 09:36 AM
Now that's a classic move, Hoff. Sorry to hear that, it makes me cringe to think that my boat actually may be running at 100 degrees.

I'll try the hair dryer trick. Just pull the sending unit, aim the hair dryer at the bottom, heat it up, and watch the temp gauge with the key on? How long do I have with the key on and the boat not running before I fry my electronic ignition?

Last question, and I know, I know, it's a dumb one. Where are both thermostats located to make sure my previous owner didn't do the same thing yours did? Thanks a million.


Pete, if you have a 351, you only have 1 thermostat.

PeteS
09-08-2004, 09:41 AM
Thanks, H2O. Silly question, but where is it located?

NeilM
09-08-2004, 09:43 AM
Given the age and unknown repair history, replacing the thermostat is not a bad idea anyway - they're relatively inexepensive and easy to replace. Once done, it's one less variable that you have to deal with..

PeteS
09-08-2004, 09:44 AM
Great, will do. Can I just pick up one at a local auto parts store for an 88' Ford 351? Windsor? 160F?

JimN
09-08-2004, 09:51 AM
If it was supposed to run cold, they wouldn't use a thermostat. If it's stuck open, there's a reason for it and it needs to be investigated. If the temp gauge is acting flakey, that needs to be checked out. If the motor is at air temperature, it shouldn't read 100 degrees unless the air temp is 100 degrees. That hardly sounds like a thermostat issue.

If the thermostat is stuck open, either it's just bad or something is keeping it from closing. Like impeller vane pieces. Remove it and look at it. If it's more than a few years old, replace it. It's not worth wasting time to save an old thermostat and gasket when it could possibly be part of the problem.

You won't have complete combustion and adequate expansion if it's not hot enough to vaporize when it goes into the cylinder. In a cold motor, low in-cylinder temperature makes it impossible to develop the power it should. If it's too hot, you have detonation and meltdown.

H20skeefreek
09-08-2004, 10:09 AM
Thanks, H2O. Silly question, but where is it located?

follow the lines from the raw water pump, they will lead to the thermostat housing. It's on the front of the motor, on top. Mine is off center to the starboard side. I think boats with indmar motors have the thermsotat housing centered?? It should have 1 line coming in and 2 lines coming out I believe.

PeteS
09-08-2004, 10:46 AM
Gosh your going to have to send me an invoice, Jim :) . Thanks for the help! Can I pick up the thermostat and sending unit at an auto parts store?

I ussually go through DIM but I'm working on the boat tonight and would like to take care if it if there are problems.

PeteS
09-09-2004, 08:29 AM
Just to fill everyone in who provided assistance, I pulled my thermostat housing apart yesterday to find that the orginal thermostat was stuck WIDE OPEN! It was corroded, and unfortunatly jammed. I replaced the sending unit as well, just because I had picked one up for $9.00, and put in a new thermostat. Let's keep our fingers crossed! Thanks again to you guys, as always, a huge help.

Thanks,
Pete

BrianM
09-09-2004, 08:47 AM
Pete,


I would make sure that you put a 142 degree thermostat in the boat. I bought a 160 from the autoparts store and it made my '88 351 run too hot (like 190-195) in the warm water (about 90 degrees) that I run the boat in. With the 142 it runs right where it should about 160.

PeteS
09-09-2004, 09:41 AM
Good idea, Brian. I picked up the thermostat at my Mastercraft dealer, and at the time of purchase the rep stated that it was in fact a 143F. Trying the boat out today to verify the changes. Thanks again.