Yanmar 6LY3-UTP oil tempertaure delta

[Steve Wells]

The port engine oil temp runs about 190 degrees and the starboard runs about 168, always a delta of about 22 degrees. My coolant temperature is the same on both engines (~162 degrees) and the oil pressure is the same (~78 #'s). I ran the engines at idle at the dock for 35 minutes and the oil temperatures got up to 119 for the port and 97 for the starboard, the same delta of 22 degrees so it has nothing to do with props imbalance. It is not a sensor or indication problem as I have had the engines thermo scanned (at the housing between the oil filters) and there is truly an oil temperature difference as described above. I had the engine cooling systems descaled/flushed with no change.
These engines are 4 years old with only 250 hours. Anyone have any thoughts on why I am having this phenomenon?

[Arthur Garfield]

First thought-thermostat springs reacting differently.Possible obstruction within cooling circuit.RPM difference. Water pump impeller damage.....some more possibilities but these seem most forward.


All the Best