Engine Temperature Differences Inboard/Outboards

B

Blue Cruiser

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Sep 16, 2006
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23441
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We have 5 liter fuel injected Volvo Penta engines, always operated in fresh water. The port engine with the original sea water pump runs at about 152 degrees F while the starboard engine with a replaced water pump runs about 10 degrees hotter since it was replaced at 840 hours. Engines have 985 operating hours and are 14 years old. When not in use, the boat sits out of the water on a lift The impeller on the hotter engine has been inspected and looks good. Could there be a little corrosion on the higher temperature gauge wire connections? Where are the temperature sensors mounted on the engines? Could the higher temperature sensor be going bad? Could the water jackets on the hotter engine be corroded. Recommendations would be appreciated
 
When the pump was replaced were all the old impeller pieces found?
 
What was the normal temp. before pump replacement? It not uncommon for the sending units to be 10 degrees different.
 
Before the pump replacement, both engines ran at the same temperature about 152 degrees. When the original pump failed due to water leak, the impeller in that pump was intact.
 
If you put the new pump on in the water, is the everything open, no kinks in the hose, thru-hull etc.
 
Try using an IR temp gun and take readings right under the thermos housing on the intake manifold. I have found with the OMC/Volvo thermostat design that this area most closely mirrors the true cooling water temp. On my '88 OMC 4.3 with the 160* stat, this area usually reads at 150-155* if the cooling system is working properly. Anywhere else on the engine or even the top of the stat housing tends to read cooler.
 
Are those temps at cruise speed? Where are you boating?
Are the engines EFI or MPI ? RWC as I suspect, or FWC?

152*F sounds (to me) a bit too cool for injected engines , particularly MPIs. The sensors need higher temps to respond properly and combustion is better at the higher temps.
Not sure whether Volvo uses a 160* or 170* t-stat, but FWIW, my FWC Crusader MPI's spec a 170*F t-stat... and run ~~167-174*F as scanned from the ECM.

I would suggest you check the t-stat spec for your model engines and test the t-stats in a pot of warming water on the stove with a candy thermometer.Make sure the cool engine's t-stat can close tightly.
 
A 10 degree difference immediately after changing a pump indicates that something changed. I would remove, inspect, and reinstall the pump. Trace your steps and see what may have changed to increase the temp 10 degrees just with a change of the pump.
 
Start with an IR temp gun to see if your temp gauges are correct. They're cheap at Harbor Freight.
 
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