Hi guys, took the boat out yesterday for a long run in the sun and after 20 minutes the oil pressure started creeping below 40psi, then within another minute or so was at 20psi, then all of a sudden dropped to zero! I was running a steady 3500rpm.

I let the engine cool for a while then limped back to the marina at 900rpm with about 5psi showing.

The engine is fairly standard and has a new slightly upgraded oil pump fitted and has had lovely pressure for the last 4+hours use I have had out of it this season.

The engine is going to have to come out I am sure, but what are your thoughts on what it might be? Am hoping not a cracked block, is that likely?

TIA

Oil level OK? No milky fluid in oil?

Senders can go bad. An engine with no oiling sounds bad pretty quick.

Wannabe

oil level was a little high and no milk, infact very clean.

put a mechanical guage on it ASAP to verify that your OEM gauge is working right. my old outlaw had a flaky oil pressure guage, it read zero sometimes at startup, i would put a jumper wire to the ground on the sender and the guage popped right up to 60 psi every time. you can buy a cheap mechanical one at harbor freight with all sorts of adapters to sanity check your gauge.

if you truley have that low of oil pressure something must be going south and it could be all sorts of reasons. if its truely low first thing i would do is pull the filter and cut it open and look for shaving, debris, ETC and drain the oil and check it for any debris also.

Quick update:

Started the boat from cold yesterday(frist time since pressure problem). Pressure immediately went to 65psi, but as the boat warmed up the pressure fell down to about 20psi hot idle. All sounding good so far, right? Sadly after reaching temp I started to notice a big end knock so will have to pull the engine after all.

Question. Do you think the knock is due to the low pressure, or do you think this might have been the initial cause of the low pressure? Don't want to pull the engine do loads of work only to find the fault elsewhere if you know what I mean!!

I think you cooked the bearing and that caused the low oil pressure. Your going to have to disassemble and these can be impossible to correctly diagnose from description only.

wannabe

Thats what I wanted to hear really. I don't know what else could have caused it.

I'm having similar issues with mine, although after a long cruise I haven't notice a drop while running, I notice a drop to 10 psi at idle speeds. When yours drops does it come up with acceleration or does it stay low?

After a cool down it did increase to a point then dropped off. I have since stripped the engine and found that all the big end bearings were shot, 3 had spun and one had hammered itself out to the thickness of a piece of paper!! i know believe all this started when i hydraulic the motor after springing a leak in one of the manifolds.

Make sure the oil pickup tube is welded to the pump housing.