Overheating 92 Nautique

[tfpoke]

My 92 has been running a little hotter for the past 4 years. I've replaced the thermostat and impeller numerous times with no change. Never trashed an impeller, no fingers ever missing. I did blow out the 4" exhaust hose on the driver's side just off the riser. Every summer it seems to run a little bit hotter than the year before.

I've checked everything on the intake side, I don't think it's sucking air. I checked the strainer the other day, and as soon as I broke the seal, water starting draining out, as though there was a vacuum. I tried running the motor with the exhaust hose off the external water pump and filled a 5 gallon bucket in about 20 seconds at 2000 rpm. I've checked all the connections from the intake up to the RWP.

I did notice the exhaust hose on the driver's side running hotter than the hose on the other side. I pulled the top of the risers off both sides and didn't find much blockage in the ports entering the risers.

The engine heats up to about 175 in idle. It's getting up to around 185 while pulling a slalom skier or jumper. Will heat up more after the ride, will cool down to around 170 if I rev it up in neutral. I'm at a loss as to what to try next. I did have one occurrence this summer where the gauge dropped to 160 for about 5 seconds, and then went back to the "normal" overheating situation. The engine has about 1100 hours on it. Thanks in advance for any help.

[WakeSlayer]

RE: Overheating 92 Nautique

What thermostat do you have in it? Marine stats are not for cars. 143 or 160, generally. My 502 stays pegged at 160, but the Mustang does fluctuate. One side will run a little hotter just because of water flow, this is not a problem. When I replaced a temp guage in the Mustang this year the place i got it from sent me the wrong sender and that gave me some very hot readings that were incorrect. Get a laser thermometer like a Raytek, and shoot the motor when it is running and see what it is really at. They are like $50 on Amazon, and a great tool to have in the box for a bunch of applications.
Also, go through all your hoses with a 5/16" nut driver. They loosen over time and need to be checked at a minimum of every year. A small air leak or two will cause exactly what you are describing, too.

[tfpoke]

Re: RE: Overheating 92 Nautique

What thermostat do you have in it? Marine stats are not for cars. 143 or 160, generally. My 502 stays pegged at 160, but the Mustang does fluctuate. One side will run a little hotter just because of water flow, this is not a problem. When I replaced a temp guage in the Mustang this year the place i got it from sent me the wrong sender and that gave me some very hot readings that were incorrect. Get a laser thermometer like a Raytek, and shoot the motor when it is running and see what it is really at. They are like $50 on Amazon, and a great tool to have in the box for a bunch of applications.
Also, go through all your hoses with a 5/16" nut driver. They loosen over time and need to be checked at a minimum of every year. A small air leak or two will cause exactly what you are describing, too.

I've been through all my hose fittings twice. The guy at Discount Marine told me I should fill a 5 gallon bucket in around 10 seconds at 3000 rpms if the intake side was working correctly. I was only able to run it at 2000 rpms and hold the hose, bucket, throttle, etc.... Filled the bucket in around 20 seconds.

I checked the thermostat and it looked fine, actually one of the three openings was slightly plugged. Cleaned it up, put it back in, no difference. Bought a new thermostat from Discount Marine and put it in with same results. They did tell me the driver's side would run slightly hotter because of water flow.

I do have some ground problems that cause my voltage gauge to run low. I grounded my perfect pass to the battery to help minimize the problem. I guess that's fairly common with the wimpy wire they run on the instrument panel. I'd be happy to find the temp. gauge was bad. I'll see if I can borrow a temp. gun from work. Most of our ski lakes are dry, but one has enough water to at least get the boat in the water while on the trailer. Thanks for the advice.

[TRBenj]

Re: RE: Overheating 92 Nautique

I checked the thermostat and it looked fine, actually one of the three openings was slightly plugged. Cleaned it up, put it back in, no difference. Bought a new thermostat from Discount Marine and put it in with same results.

Like Mike asked, what thermostat do you have in there. My PCM's with the 143 'stat run at 155-160. My understanding is that the 160 'stat would have it running right around 180. If thats what you have installed, then Id say your temps are normal.

[WakeSlayer]

RE: Re: RE: Overheating 92 Nautique

It was suggested to me to drill a little weephole in the plate of the thermostat to steady out my temp reading. Once I detemined that it was within range, and safe, I trust my gauge now.

On another note, I need to do what you did with the PP ground on my Super Air. I have some PITA voltage issues that I want to get resolved this fall before storing for the winter. Niothing that keeps me off the lake, but anooying, for certain.

[tfpoke]

Re: RE: Overheating 92 Nautique

I checked the thermostat and it looked fine, actually one of the three openings was slightly plugged. Cleaned it up, put it back in, no difference. Bought a new thermostat from Discount Marine and put it in with same results.

Like Mike asked, what thermostat do you have in there. My PCM's with the 143 'stat run at 155-160. My understanding is that the 160 'stat would have it running right around 180. If thats what you have installed, then Id say your temps are normal.

I have the 140 thermostat in there. My boat used to run around 160 all summer long. Every year it runs hotter and hotter, at least according to the gauge. I did notice one 5 second period this summer where the gauge dropped to 160, making me think it could be something electrical. When I blew out the exhaust hose last summer, made me think it really was running hot. Thanks for the help.