Bruce in Bangkok wrote:
I nearly went crazy trying to solve a similar problem after a fellow
ran aground on a mud bank. Finally discovered the heat exchanger tubes
full of mud after someone told me the boat had been aground and I
noticed there was no inlet strainer.

Also the heat exchanger tubes can get slowly clogged with marine buildup
so the engine eventually starts to run hot. The problem seems to just
appear suddenly so its easy to misdiagnose, and can appear in older
engines as a drop in oil pressure due to the higher engine temp. I am
working on an engine now that this has happened to. There are some
commercial products to clean this growth out. I have this heat exchanger
pickling in Rydlyme Marine solution which seems to be working, but I
suspect most of the products are the same.
Red

You did not say what the pressure is at idle.

Does the guage read when idling? Some manufacturers allow a very low
pressure when hot idling. I will check my engine manual next time I go to
the boat.

50 psi when running seems quite OK.

Alec


"hookipa" wrote in message
ups.com...
I recently moved my boat from New Zealand (cold water) to Tonga (very
warm water) and I am now experiencing very low oil pressure at
operating temperature at idle. The engine is a Volvo Penta AD31B and
I am not sure of the hours on the engine. As the engine has seperate
circuits for the oil warning light and the gauge, I believe that the
problem is not the gauge/sender. At operating speed i get about 50
psi, but at idle it sometimes turns on the warning light. Any
thoughts or checks before I pull the boat and remove the engine to
check the main bearings and oil pump?

I do not know if you have the manual with you but the manual online at
volvo, states engine hot idle pressure 21 psi and full power hot 60 psi. It
does not say max or min so I assume this is typical.

Oil grade CD 15/40.

Alec


"hookipa" wrote in message
ups.com...
I recently moved my boat from New Zealand (cold water) to Tonga (very
warm water) and I am now experiencing very low oil pressure at
operating temperature at idle. The engine is a Volvo Penta AD31B and
I am not sure of the hours on the engine. As the engine has seperate
circuits for the oil warning light and the gauge, I believe that the
problem is not the gauge/sender. At operating speed i get about 50
psi, but at idle it sometimes turns on the warning light. Any
thoughts or checks before I pull the boat and remove the engine to
check the main bearings and oil pump?