chrysler nissan sd 22 fluctuating oil pressure

[Shala]

gday fleet
i have a chrysler nissan sd 22 marine diesel engine with fluctuating oil pressure.
the pressure is solid for the first 1-1.5 hours of operation and then it begins to fluctuate or flicker on the gauge. a change in rpm up or down seem to stabilize the pressure for a short period and then it begins to fluctuate again. any ideas as to what might be the cause and how to repair.
thanks in advance to all the diesel gurus out there.

[Lepke]

Could be low oil level in some heeling positions, a weak oil pressure relief valve spring, oil pan could have some crud occasionally partially blocking the intake screen, bad gauge or sender - check with a mechanical gauge at the block.

[markbarendt]

In any trouble shooting situation eliminate the easy (doh!) stuff first. Most people jump ahead too quickly.

Oil level truly full?
Is the oil discolored?
Then
Change oil and filter and check back.

[Compass790]

Originally Posted by Lepke

Could be low oil level in some heeling positions, a weak oil pressure relief valve spring, oil pan could have some crud occasionally partially blocking the intake screen, bad gauge or sender - check with a mechanical gauge at the block.

wot Lepke said AFAIK

[a64pilot]

I’m betting the gauge, connect an inexpensive direct reading gauge and give it a try.