Engine runs hot with T'stat installed

[justinteoc]

I have a 97 3.0 GSMLKD and when I purchased the boat last year it did not have a thermostat installed so after reading that it does need one I purchased one and installed it we'll at cruising speed the temp will continue to rise and when I come to idle it will sloooowly return to normal and if I remove the thermostat it will only run about 110 even a wot. I have replaced the manifold but not the riser and the riser is not completely stopped up but I can tell it's kind of stopped up but if it's running cool without T'stat wouldn't that tell me it's not a riser restriction? Also the T'stat is a Sierra not oem but it is working correctly? The T'stat housing is a little rusty but not bad enough to be restricted.. So I'm lost I'm thinking about just leaving it out and stop worrying about it......
Also it has a brand new sea water pump and it is definitely timed perfect..

 

[jerryjerry05]

Re: Engine runs hot with T'stat installed

They're designed to run at a certain temp.
They'll use less gas and last longer.
Since it's only overheating when the thermo's installed,I'd check the small passages in the thermo housing for blockage.
Maybe it's time for a riser?

 

[alldodge]

Re: Engine runs hot with T'stat installed

I have a 97 3.0 GSMLKD and when I purchased the boat last year it did not have a thermostat installed so after reading that it does need one I purchased one and installed it we'll at cruising speed the temp will continue to rise and when I come to idle it will sloooowly return to normal and if I remove the thermostat it will only run about 110 even a wot. I have replaced the manifold but not the riser and the riser is not completely stopped up but I can tell it's kind of stopped up but if it's running cool without T'stat wouldn't that tell me it's not a riser restriction? Also the T'stat is a Sierra not oem but it is working correctly? The T'stat housing is a little rusty but not bad enough to be restricted.. So I'm lost I'm thinking about just leaving it out and stop worrying about it......
Also it has a brand new sea water pump and it is definitely timed perfect..

+1 agree you should have the thermostat installed. How hot is it getting with the thermostat installed? When was the last time the water impeller was replaced

 

[redneck joe]

Re: Engine runs hot with T'stat installed

what temp is your thermostat set to open at and as asked what temp is it hitting? Also, where are you and what is your current surface water temp?

 

[justinteoc]

Re: Engine runs hot with T'stat installed

I just purchase the riser and oem T'stat the it should be here next week... It's a brand new sea water pump so impeller is new.. It's a 160 degree T'stat and just idling it stays at 160 and cruising speed it steady climbs I stopped at 210 and the lake water was probably 65 degrees in mississippi...

 

[justinteoc]

Re: Engine runs hot with T'stat installed

The riser definitely looks bad even if it does not fix temp problem it definitely needs it

 

[raven1978]

Re: Engine runs hot with T'stat installed

I would check the bypass port in he t stat housing for a piece of impeller lodged on there. Had same issue on a boat i was working on and this was the cause. Might not be in your case but worth a look while its off.

 

[alldodge]

Re: Engine runs hot with T'stat installed

Engine runs cool without the thermostat
Engine overheats with the thermostat
When the engine heats up the thermostat would be full open allowing water to pass easy, but the engine still overheats. If it was the risers, even though they look bad it should be overheating with or without the thermostat. My thought is either something is blocking water flow in the housing when the thermostat is installed (not installed correctly, something is missing), the engine circulating water pump has a problem (vanes missing or loose on the shaft), or prior owner change something which is being over looked.