I have a SBC with about 1100 hours on ot and recently it developed a low/ no oil pressure after a change. I have a sender for alarm and gauge and both read zero so I think it's true. Oil pressure is ok otherwise. Even after boat sits builds pressure in like 2 seconds and is like 30psi hot at idle. But even with filling filter to the top it took 25 seconds of idle to build pressure. Thoughts?

filter collapsed, try a new one

not fram wix if you can get

I should have given that info. It has done this the past couple oil changes and I have used a fram(I know), a STP and a Bosch and all reacted same. It's weird because only does it after a change. I figured it was about to blow up but I have out like 75hrs on it since I noticed it .

what brand&weight oil did you use?

Rotella 15w-40 in it now. Was castrol 10-40 I think last oil change.

the rotella is good oil.did you check it with a mechanical gauge?you might have a sending unit going bad.

I thought of that too but I have a idiot light and a gauge and they agree there is no pressure for a while so doubt both could be bad.

maybe rebuild time.

What engine model and year ? What are your oil filter numbers that you are installing ? Fram and STP are junk filters as I would not use neither for any boat app. Just saying.

Your info says a 1999 and I have to ask you about a lite for low oil pressure on your boat at the dash - What set up is this ?

I was going to say test oil pressure with mechanical gauge as well. Possible oil pressure sender or even oil pump priming issue or worn especially with 1100 hours on the engine. What is your oil pressure running at 4200 rpm's and above ? Hopefully its higher than 30 psi ? If not U might have some internal wear problems

After oil change and no reading of oil pressure what rpm range is this taking place at ? what happens if increase rpms does it then pick up oil pressure readings ???

Any internal engine noises and or knocking ???

I would test with a mechanical gauge before anything else and maybe try different oil filter brand and correct model #.