I have a 2004 525 EFI and just this past weekend noticed my oil pressure gauge reading funny. Normally it is around 35-40 at idle and 60 when over 3000 rpm under normal operating temps...now it is reading basically the same at idle and 3000 rpm... 55 psi (idle) 60psi (3000 rpm).

I have only put the boat in the water last week. I am pretty sure then that the oil pressure was correct at idle.

Headers are new, and the oil, filter were all changed end of season last year and probably haven't put any more than an hour on the motor this year. Filter is a Napa 1060. Oil looks good (Merc 25w40). Engine temp is around 165.

I am thinking I will change out the filter since that is the cheapest and easiest to do but doubt it will change anything.

Could this be a sign of a bad oil pressure sensor? Would it still fluctuate if going bad (5 psi difference).

Does the gauge go to "0" when you shut it off? Do you have access to a scan tool? If so, you can verify the oil pressure to see if it's the same as the gauge. The ecm has a separate oil pressure sensor that gives it a pressure reading.
If you can't get your hands on a scan tool, then you can hook up a mechanical gauge to the engine to see if it jives with the gauge on the dash. Check that out and get back to us.
Eddie

Yes, gauge goes to zero when shut off. I should have access to a scan tool late next week.

Got the scan tool this weekend. After idling the engine for a little bit, here is what I saw on the scan tool.
Engine temp was 145 degrees F.
Oil Pressure at 755 rpm was 52 psi.
If I increase the RPM to a little over 1500, oil pressure goes to 61 psi.

New oil filter was installed but made no difference.

Also, since this is the first time on the scan tool, I am curious on a few fault codes that showed up.

These codes were checked at idle or with the engine off.

#94 Pitot Pressure (boat speed sensor) low
#74 Fuel level 1 circuit high
#118 Steering postion circuit high
#191 Fuel level 2 circuit high



Any help would be very appreciated.
Thanks

I think the codes you have there allways come up as you are not hoocked up with those sensors .

Sounds like the oil pressure sender may be failing

Those codes are always set if you do have the those apps for a ECM / PCM engine. I wrote the reasons to why in a past post up here. .They mean nothing unless you have them.

Thanks for the replies...that's good to know about those codes.

I have another sensor I can try this weekend.

Question regarding the scan tool, can they measure sea water pressure? I looked when I had it plugged in but didn't see anything showing sea water pressure.

It's a Rinda TechMate Pro Scan tool.