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Engine Coolant Temp Warning Light


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Came on after an hour + worth of riding as we were crawling back to the dock to drop a few folks off. After we dropped them off the warning went away after startup and no indication as we crossed the lake until we slowed down to put it in the slip. Lake temps around 70 deg but not sure what temp the boat was running at. I suppose I could check the transmission cooler and impellar as a start.

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Its too bad you did not see what the engine temperature was at when warning alert activated (which is usaually 200-210 degrees)? I would start with the impeller, when was the last time you replaced it? how many hours are on the current one in the boat?

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I just picked up the boat this month on a private sale so no idea if it has ever been changed. I'm assuming it hasn't ever been based on other things I'm seeing with it. 135 hours on the boat.

Question. How do you clean the transmission cooler? Just detach the upper and lower water hoses but leave the transmission lines attached? I heard someone comment on using needle-nose pliers to pull debris out but never having done this I'm too sure how it's done.

Thanks for the help.

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Up early and over to the dock by 6am because I've become those weird old guys my kids make fun of all the time...Ran the boat for about 20 minutes with the temp getting up to 168 then dropping back down to 160 when the t-stat opened up. It did this several times before i shut it down.

No leaks as the bilge was done dry. I'll still inspect and replace the impellar and also take a peak at the t-cooler.

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Good news on your temperature, that is exactly where it should be. If impeller is intact chances are good there is no debris in your cooling system. I change my impeller every season, regardless of how many hours are on it. It is cheap insurance and we all know the consequences if you have one destroy itself.

Have you ever pulled one out? I use a small pair of vise grips to lock onto the impeller after soaking with wd 40. Another trick I learned is to mark the cover before removing to make it easy to align back up when re installing. Also, the four screws are brass no need to crank them down excessively tight... they will strip out.

Edited by Fman
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Fman, thanks for the assist. I've pulled impellers in the past with an impeller tool so a bit of experience there. I do like the suggestion of marking the cover for re-assembly. Last time I pulled one off my Supra it took longer to realign it than pull the impeller plus there's not a lot of room back there on the older Supras. I already have an impeller on the way from Skidim.

Still wondering why we had a Engine Coolant Warning. Lots off debris in the water from recent heavy rains so perhaps I had/have some clogging. I'll be sure the check the temp gauge next time as well.

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Update. Just went out to give my son a pull. Went about 1/2 mile and the Coolant Temp Light popped on again. Engine temp 207. Lots of over heating smells. Allowed the engine to cool then started it up and temps went back up over 185 pretty quickly before I shut it off. Let it cool again then started it up and it went up to167, then dropped back down to 160. It did this cycle a few times so I we limped back to the dock.

At one point on the way back to the dock I sped up a bit to see what would happen to the engine temp and noticed that the temp went to about 185, then it seemed as if the thermostat opened as the water temp dropped all the way back down to about 145. Pretty big temp swing. Perhaps the thermostat got stuck open as well as closed.

So you know, we also checked the water flow before and after the transmission cooler by unhooking the hose connections and starting the engine, good flow before and after the transmission cooler so I'm assuming it isn't clogged and the impeller is working. I plan to replace the impeller regardless.

My diagnosis is that the thermostat is sticking some of the time and needs replacing. Concur? And do any of you have other thoughts about what I should also consider or check?

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