Overcooling

[stu man do]

I have twin 2001 Volvo Penta V-6's 4.3 GI PEFS. One engine warms up to 175 degrees within a few minutes, the other never budged off of 100 degrees. I switched temperature sending units with no change. I then replaced the the thermostat. Slight change happened when I did this, at idle the temp. goes up to 130 degrees, but when increased to 2,000 rpm's it drops back down to 100 degrees. The stat I installed was 160 degrees. Anyone have this problem, and what else can I try? The guage does jump up a bit when I turn the key on, and now it moves to 130, so I am assuming it is not a bad guage.

 

[JustJason]

Re: Overcooling

don't assume anything.....

get an infrared pyrometer and shoot the block where the temp sender screws in. shoot the tstat housing as well incase you don't get a good reading from the first place,
compare what the meter says to your gauges, betcha you'll find something interesting.

 

[stu man do]

Re: Overcooling

Are you thinking the guage is wrong and the engine is running at the right temp.? I forgot to mention that the engine that is overcooling only maxs out at 4,000 rpm, while the other does 4,300 rpm or better.

 

[JustJason]

Re: Overcooling

Are you thinking the guage is wrong and the engine is running at the right temp.?

Yes, that would be the first thing i would check. you should verify what the gauge is telling you is correct or not.
could possibly be the same issue with the tach's also. but then again could also be a billion other things.

 

[stu man do]

Re: Overcooling

Thanks, I am bringing home an infrared pyrometer from work tomorrow and will check it out. I will let you know what the outcome is. Appreciate the advice.....this just has me stumped.

 

[stu man do]

Re: Overcooling

I was able to check the temp. on the engine yesterday and got the following readings. Thermostat housing 85-98 degrees, hose exiting housing the same, exhaust side manifold 130 degrees. The other engine has readings about 30 degrees hotter in all locations. The temperature did not go up at all while running the engine as it did last week after replacing the stat. My next replacement part is the gauge, I noticed out of all my guages on the dash, the temp. guage is fogged up for a while after I uncover the boat. But.. with the engine readings I am getting on temperatures, it should not move?
Does anyone know if running an engine that is overcooling hurt the motor?
Maybe the new stat I installed is faulty, might as well replace it again too.
I will say that the engine runs really good, it just does not get the max. rpm like the other engine.

 

[jerryjerry05]

Re: Overcooling

Over cooling ain't bad but the motor is supposed to operate at the 160 or what ever it's spec'd at.Something about oil viscosity.Too thick or thin.
Switch wires on back of guages before you buy new.Then start.
Put a remote tach on your motors to see if there is that much of a difference.
If there is a difference,then check props for damage,make sure they are the same size,same manufacturer.Make sure they weigh the same.
Hitting something in the water (sandbar,mud) can bend all three blades and change the pitch.Lots to look at.Jerry