91 Sport Nautique Temp Issues

[atolman]

Hey all, newbie from Charlotte to this site and been lurking for a while. Great information around here!

Anyway, bought a 91 Sport last summer and it has been a blast. Got it out from being winterized this past month and it's not running at all like it did when I bought it. My temp gauge stays really low, like around 100-120, when underway or idling. If we've sat for a bit and I turn the key without starting the temp jumps up, but then quickly returns to 100-120 as soon as I start the engine.

I'm assuming thermostat is stuck open? I ordered a new thermo and impeller from skidim so I'm going to see if that solves it. Anything else I should look at? I'm afraid I might have a torn up impeller and a piece is in the thermostat housing causing it to stay stuck open. Where else should I look if there are pieces of impeller all over?

It's also spitting lots of white smoke. Maybe steam since the temps are running so low?

[s_kelley2000]

Sounds like it could be a stuck thermostat causing it to run cooler but not sure it would run that cold. Although if the lake water is still pretty cold I guess that would make sense. If you are missing fins when you swap the impeller then the most common places they end up seem to be the transmission cooler and thermostat housing. If they were stuck on the transmission cooler you would probably be running hot due to the restricted water flow. The white smoke could be steam but tough to say for sure.

[atolman]

Well now I'm stumped. New impeller and mew thermostat put in and temp quickly went up to 200 right after I launched. Limped back to the ramp and puller her out.

What now? I went through all hoses and tightened everything. Don't see anything leaking.

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[Mamigacz]

It is possible (because I did it once) to reinstall the raw water pump backwards. The flow will go out of the engine instead of into the engine.

When you replaced the impeller, did it have torn veins?

If you reinstall the old thermaostat does the orginal condition (colder than normal readings) return?

Its a long shot from the symtpoms you described, but it wouldn't hurt to test the temperature sender. I can get you a proceedure if your interested.

[atolman]

Definitely marked the pump before I took it off to be sure I didn't install it backwards. I could tell for sure it was pumping because the new gasket for their thermostat didn't sit right the first time and water spewed everywhere when I put it in the lake. Reinstalled the thermostat with a small bead of liquid gasket and it sealed up fine. The old impeller was perfect but I installed the new one anyway.

Haven't tried putting the old thermostat back in yet but I guess it's worth a try to see if it goes back to running cold.

Also going to go through and replace all hoses as some look pretty old.


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[atolman]

So I'm still stumped on this thing. I have the boat in the driveway and hooked up a hose and a big barrel of water into the intake side of the strainer for troubleshooting.

All hoses are tight, strainer is good, new impeller, thermostat.

Temp gauge still goes up in between 180 and slightly over 200. I can hold my hands on both manifolds and they're warm but not that hot. Thermostat housing is cool to the touch as well so it doesn't seem like it's getting that hot. What next?



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[s_kelley2000]

I wonder if your gauge is faulty. If you have access to an IR temp gun I would use that to check to see what temps the block is actually giving off.

[atolman]

Okay I feel like an idiot. Cleaned off the temp sensor as it looked dirty and messed around with gauge and it now sits right at 160 or slightly less. Wooo! Next is to get it on the lake and be sure it does well at higher rpms

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