2000 ski nautique..overheat under load

[nzltmp]

Have a 2000 ski Nautique that overheats when pulling a skiier.
changed impeller. returns to normal quickly and won’t overheat when in idle or under low power…also doesn’t overheat when pulling a tuber.

runs perfect outside of that/no engine miss

water strainer is clear of debris

suggestions???

[nzltmp]

SOLVED

YEP..stuck thermostat.

buddy removed it and went to explain to his son how one works…it was stuck. Thank you all for the direction. What a great forum!

[SilentSeven]

Many cooling issues are solved by ensuring there are no air leaks in the intake side of the raw water feed. I'd start there - check all hoses and clamps to make sure they are clean and tight. Also make sure your strainer oring is in good shape.

If that does not solve it, I'd remove the engine thermostat and run it without one and see if anything changes.

My guess - you have an air leak that only shows up under higher suction levels you'd tend to experience at high RPMs. It's also possible you have a thermostat that's not fully opening.

Sent from my Pixel 7 using Tapatalk

[Michael Crouse]

You may have some plugged ports from a blown up impeller. My 2000 sk inatique had parts of an impeller around the thermostat. Heat would creep up when skiing. Might be with clearing all the areas around your thermostat and all your hoses coming off the water pump.

[peteb]

Agree with previous posts. Make sure your not sucking air and if you haven't changed the Tstat in a while its a good time to do that. Make sure to get new gaskets also when you order the stat.

[jpwhit]

It's not likely an air leak. Air leaks typically behave the opposite of what is described. Overheat at low speed, get better at high speed.

Most likely it's a worn-out thermostat that just doesn't open wide enough anymore.

Less common, but causes the same symptom, back around 1998-2000, there was a batch of defective GM Marine circulating pumps produced. The metal impeller wasn't properly press fit to the pump shaft. Then with enough age, the impeller would start slipping on the shaft.

[Jonny Quest]

I concur with jpwhit. My Spidey-sense says T-stat.

JQ

[nzltmp]

Thanks everyone
replacing thermostat today..will advise on results.

btw. Lake impeller replaced last year..old one didn’t come apart…so no clogging of passage ways

[nzltmp]

SOLVED

YEP..stuck thermostat.

buddy removed it and went to explain to his son how one works…it was stuck. Thank you all for the direction. What a great forum!

[SilentSeven]

Thanks for posting your fix! Great to hear you are back up and running.

Sent from my Pixel 7 using Tapatalk