Temperature Fluctuation

[StefanMoore]

Hello. We have a 01 Outback V. The engine was rebuilt a couple seasons ago and has been running weird since. Since the boat was rebuilt the engine temp will go up to about 190-200 and them go down to 155ish. It does this pretty rapidly and we have tried to replace the thermostat with an automotive and a marine thermostat. If we take the thermostat out and run the boat the boat will stay steady at a 145ish temp and never climb. Is this something that anyone has seen? We are working on trying to figure it out.

Thank you!!

[Stazi]

Your engine water pump might be going bad. Not the raw water pump.


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[StefanMoore]

Thank you much! We will give that a try next. We have been messing with it a bunch. Hopefully this will get it back running good!!

[DOCDRS]

I assume you have a new impeller, and the stat is a 160 degree. When is it 190 and when is it 155, and how long does it take to get it to 155 and what if you neutral rev it at 190?

[JHutch]

I am having a similar issue. Put a new thermostat in last year and now I am getting fluctuation. At idle I can get to 190 give it a little throttle and it will instantly drop and stay low. Sometimes it drops to like 120. I am wondering if I have sensor issue? As in its reading incorrectly? Before I changed this thing would never budge off of 160.

[zabooda]

Could be a partial blockage.of your intake hose. When moving the hydrostatic pressure is much higher than the raw water pump.

[james yarosz]

JHutch,did you ever figure this out,my 2003 outback is doing the exact same thing.Used to run about 170 all the time,now after thermostat change the temp moves around from 180 to 140.Doesn,t seem to be related to any certain speed or rpm.Boats feels like its running fine.

[Branden967]

JHutch,did you ever figure this out,my 2003 outback is doing the exact same thing.Used to run about 170 all the time,now after thermostat change the temp moves around from 180 to 140.Doesn,t seem to be related to any certain speed or rpm.Boats feels like its running fine.

Are you sure a 160 degree thermostat was put back in? If it’s not going above the 180 mark, was a 180 thermostat put in by mistake?

[james yarosz]

Im not sure if it was a 160 or a 180,the problem is the temp fluctuates from 140 to 180.It doesn,t hold steady at one temp like it used to.

[Fossenrf]

Did anyone figure this out? Having a similar issue with my 03 Outback LS.