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What would cause low oil pressure...

Jim14560
Guest Contributor

What would cause low oil pressure on an 8.1L Mercruiser? The starboard engine is suddenly reading 35+/- PSI. It’s normally 60+/-  Oil pump? Oil level is OK and no sign of a leak anywhere in the engine compartment. 

3 REPLIES 3

wingless
Rising Contributor
Diagnostics w/ a mechanical oil pressure gauge is "easy". Get a 0-60 PSI mechanical (dial) gauge, short tube, and tee fitting, all 1/8" NPT.

Remove existing pressure sender, insert tube into block hole, attach tee, then new mechanical gauge and existing sender.

Operate engine. When oil pressure fluctuates observe mechanical gauge. If mechanical is good and dash fluctuates, problem is probably a bad electrical connection.

This happened on mine. Turned out to be those right angle push on electrical transducer connectors. It was snipped off, replaced w/ the correctly sized and properly attached marine ring tongue connector, retained w/ correctly sized washers, lock washers and nut.

It has been fine for over a decade.

Jim14560
Guest Contributor
Thank you.

clowenthal
Guest Contributor
I had the same issue. Ended up being my manifold needed replacing. I first tried the oil cooler but that wasn’t it. Check your oil - it may be getting salt water in and becoming a little milky.