Need help with oil pressure question.

maxum26

Cadet
Joined
Aug 7, 2011
Messages
6
I have a 2001 mercruiser 5.0 L MPI I'm running mercruiser 25-w40 oil i noticed the other day my oil gauge dropped from 40 psi to around 20 psi at idle. While under load its at 42-50 psi but if i cut back on the throttle it immediately drops to 20 psi then works its way back up to around 40 .I had a marine mechanic put a mechanical gauge on it and he says everything is fine and that its in the normal range between 35-60 psi.My question is why all of a sudden has the gauge started acting up i already replaced the sending unit and I'm still having an issue. Any help would be greatly appreciated.
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Need help with oil pressure question.

Like anything else made by man, they fail sometimes, and it always happens "suddenly" one day it works, next time it doesn't.
 

Rocky_Road

Lieutenant Commander
Joined
Oct 8, 2008
Messages
1,798
Re: Need help with oil pressure question.

The minimum oil pressure at idle is 4 psi, and that is where the low oil pressure switch is set. At 2000 rpm the oil pressure should be between 30 and 60 psi.

You are just fine with what you are seeing, and your mechanic has verified this.

Go boating...and have some fun!
 
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