Can anyone suggest what action ( if any ) I should take based on the following observations:

1. My port engine (stock Merc 454) under normal conditions shows an oil pressure reading on dashboard guage around 38.

2. After running for an hour or so at around 3800 rpm I come back in to dock and at idle (approx 700 rpm) the port oil pressure guage is going high off the scale 90+

3. If I (gently) rev up the engine in neutral, oil pressure falls.

Since the starboard engine is not showing this behaviour I assume that something is wrong.

Rich S.

Rich , This is kind of a stab in the dark , but try changing your oil filter. Next I'd try the sending unit. If you don't want to waste the money , just swap with the other engine and see if trouble follows the sender. I have a similar problem. Both engines will be 45-50 lbs at 3500rpm and the starboard one will begin jumping around from 50 to 80 (never goes any lower). Its jumping too fast to be a pressure problem , more likely the sender. Leave them come back to an idle and they both settle on 35-38 and steady.
Good luck

The first thing I'd do is put a local guage in the block and compare. If it reads normal it's most likely a sender problem.

DAVE

oil pressure should work oppsite,of course.....it might be a bad filter....kinda iffy.....did see this once,a customer installed an automotive sender in his boat,but didnt realize they accually work backwards......at 10 psi on a manuel guage the electric was at 90+....at 80 psi the electric was at 10-.......just a thought

Rich , Let us know what yo find , Inquiring minds want to know

Thanks everybody for the suggestions. Another friend has suggested that I have a positive short. He says that if I tap the guage it ought to swing back down. He sounds very definite about this. It will be Saturday before I can get back to the boat. I will definitely post whatever I find out.

Rich S.

I think your friend is right, sounds like a ground
problem to me.