5.7 Mercruiser Thermostat Replacement Problem

[bharrod]

I have a 2000 Mercruiser 5.7. It was gradually overheating so I replaced the thermostat (OEM 160 degree), sleeve, and gaskets. Now, it runs at about 100 - 110 deg. like the thermostat is wide open. Every few minutes it increases fairly quickly to 170 deg. (as if the thermostat closes) and then falls back to 100 - 110 deg. rapidly (as if the thermostat opens again). Repeats constantly. It doesn't stay at a constant temp as I would expect. Anybody know what I did wrong here

 

[madurodave]

Re: 5.7 Mercruiser Thermostat Replacement Problem

as long as it doesnt get above 180 or so, I wouldn't worry about it.

 

[TilliamWe]

Re: 5.7 Mercruiser Thermostat Replacement Problem

I'll guess that you installed the thermostat on the wrong side of the sleeve.

I would worry about the wild temperature swings, for sure. it's not supposed to do that, and it shouldn't. It ain't right, fix it.

 

[captalny]

Re: 5.7 Mercruiser Thermostat Replacement Problem

I'll guess that you installed the thermostat on the wrong side of the sleeve.

I would worry about the wild temperature swings, for sure. it's not supposed to do that, and it shouldn't. It ain't right, fix it.

Just wanted to say thanks for your Excellent Trouble-shooting analysis.

My Son replaced the Thermostat on my 350 Mag and I had the Same Problem as bharrod

Sure Nuff, He installed the thermostat on the wrong side of the sleeve.

Thanks Again
Capt Al