Running to cool?

[Iamwildman]

I don't really understand this but here is the situation. I have twin 5.0GI volvo pentas. Two weeks ago I noticed my port side engine was running on the cool side, *around 120-130.
I picked up a new thermostat and replaced the old one. On my test run I noticed on idle it seemed to be climbing up just like the starboard engine, but as soon as I start to bring up the RPMs and get on plain the port side temp drops back down to in the 120s. I did notice a piece of rubber in the housing around the thermostat so I think the impellers are ready for a changing but that doesn't explain why the temp drops. I did pick up some new impellers so I'll do that on the weekend.
*Any ideas why its running cool? And would running cool effect gas mileage?

 

[BRICH1260]

Re: Running to cool?

My 5.0 GXI runs cool also, usually arounf 120-130. It did all last year and this year. I`ve replaced the thermostat twice, still same thing. Have run out of options and have at least for the balance of this year, just decided to go with it. Engine seems to run fine. If you figure it out, let me know.

 

[dypcdiver]

Re: Running to cool?

My 5.0Gi stays at 120/130 deg C unless at WOT for a a while, when it will creep up to 140 deg C and stay there until I slow down. It has been like this from new (12 years) and I have replaced the thermostat twice and it has made no difference. I don't have a IR temperature gun but it never gets too hot to be unable to place a hand on it. Engine produces fumes from the exhaust that smell to me as if it is running rich. Otherwise it runs and starts just fine. If you find a solution please post back here.

 

[boatguya1]

Re: Running to cool?

Possible debris in bypass passage in therm hsg. allowing pressure from waterpump to blow open the thermostat.

I don't really understand this but here is the situation. I have twin 5.0GI volvo pentas. Two weeks ago I noticed my port side engine was running on the cool side, *around 120-130.
I picked up a new thermostat and replaced the old one. On my test run I noticed on idle it seemed to be climbing up just like the starboard engine, but as soon as I start to bring up the RPMs and get on plain the port side temp drops back down to in the 120s. I did notice a piece of rubber in the housing around the thermostat so I think the impellers are ready for a changing but that doesn't explain why the temp drops. I did pick up some new impellers so I'll do that on the weekend.
*Any ideas why its running cool? And would running cool effect gas mileage?