Strange oil pressure

[brodie123]

Mercruiser 4.1L inline 6

What has been done and tested:
Water pressure is good - lots of flow
New oil pump, filter and oil
Cleaned out the Pickup tube

Issue:
Runs for first hour or so 100%
Oil pressure slowly starts to drop
Oil press eventually reads very low and then the temp goes up (typical low oil press issue)
Oil level is fine - even a tich above full line

What the heck??

 

[dubs283]

possible culprits:
-worn main/rod bearings
-faulty gauge(s)
-electrical issue causing false readings at gauge(s)

have you verified engine temp is actually rising (ir temp tester) and oil pressure is actually dropping with a mechanical gauge?

 

[brodie123]

possible culprits:
-worn main/rod bearings
-faulty gauge(s)
-electrical issue causing false readings at gauge(s)

have you verified engine temp is actually rising (ir temp tester) and oil pressure is actually dropping with a mechanical gauge?

No but I think those are logical next steps. Strange for them to fluctuate like that tho. I'm going to check the oil channels and maybe try a different oil.

 

[brodie123]

No but I think those are logical next steps. Strange for them to fluctuate like that tho. I'm going to check the oil channels and maybe try a different oil.

Thank you btw

 

[Scott06]

Have you verified the oil pressure with a mechanical guage? Same with temp

 

[brodie123]

Have you verified the oil pressure with a mechanical guage? Same with temp

oil pressure was verified simply with the thumb over the hole technique but it's the temp going way high that indicates it's not gauges as you can tell the engine is indeed hot.

If the rod/main bearings were the culprit, would we not hear the obvious knock?

 

[brodie123]

oil pressure was verified simply with the thumb over the hole technique but it's the temp going way high that indicates it's not gauges as you can tell the engine is indeed hot.

If the rod/main bearings were the culprit, would we not hear the obvious knock?

As a short term fix, is there an additive that we can add to the oil to increase viscosity?

 

[Scott06]

oil pressure was verified simply with the thumb over the hole technique but it's the temp going way high that indicates it's not gauges as you can tell the engine is indeed hot.

If the rod/main bearings were the culprit, would we not hear the obvious knock?

Thumbover what hole? Not familar with measuring oil prssure that way.

Yes if bearings were bad or you had low oil pressure it would make noise either from bearings or valvetrain as lifters bleed down.

Ive never seen a connection between oil pressure and temp. Had cars with very low oil prssure due to high miles run at temp no issue.

You can run a heavier weight oil or add stp or lucas

 

[Scott Danforth]

You are most likely overheating. That is dropping oil viscosity.

Get proper mechanical gauge and do a proper oil pressure test

Get an IR thermometer and diagnose the temp properly