First off let me say I have nothing but great advise from this forum.

Here's the problem, got the boat out today for the first time of the season. Everything was going I looked down and my left motor was reading 0 -5 psi on the oil pressure gauge. I shut the the motor down. Then pulled over and restarted it started fine no knocking or any funny noises. But no oil pressure. So I limped in on one motor.

Any ideas

Steve

start with removing the oil pressure sending unit on the engine and install manual gauge and fire it back up to see if you have pressure..if it does then the sender or gauge is bad,,swap senders with other engine and see what happen's..

Steve, a number of years ago I was running our family boat -- nothing at all fancy - in fact it was a straight 6 -- 165 hp mercruiser. It was very hot outside--- well in the upper 90's. We went over a larger wave and the oil light came on and the pressure went to zero. I immediately stopped the engine and we were towed to the dock. I checked the oil and all was full --- I restarted the engine-- started right up but still no oil pressure. I took the boat to our marina/mechanic thinking the worse -- The next day called and asked for the bad news. He told me there was nothing wrong with the engine -- the oil broke down. We always used straight 30 Rotella but was told that Merc changed the requirments and I should have been using 20W 506. That was about 10 years ago. We sold this boat this spring and all was well.

It could be something as simple as the pressure sending unit.

Hope all the best

3pointstar

I lost pressure last year in my rebuilt 502. Turned out to be the sending unit. It had a press on style of connector which went to the gauge. To be on the safe side a t'ed in a manual gauge so that I now have a back up gauge. If my electric gauge goes down I can look at the manual gauge on the rear deck.

I'm planning to do the same thing with the water temp. gauge . Best of luck.

I agree with checking the sending unit. Could also be the wiring up to your gauge. I have manual gauges on mine as back ups and one came in handy once when chasing an electrical issue.

Its also possible that you dropped the pick up tube on your oil pump. That happened to a friend last summer with a boat he had just bought. The tube slipped out and was laying in the bottom of the pan.

Grounding issues will drive you crazy too. Make sure theres a good ground on the sender using a volt meter.

Checked sending unit even replaced it. Checked gauge worked fine. So I fired the motor and no oil up top anywhere. But no funny noises. So I shut motor down and begun the motor removal process

Oil is fresh clean and golden.

Steve

I always verify with mechanical gauge as stated.

If you really have no pressure,,,,
It's an 85 boat so engines have probably been rebuilt at some time.

Hopefully it was the oil pump pickup that fell off the pump or oil pump rod. For pick up Get a bolt on deal or have it brazed on. For oil pump rod get an ARP or equivalent strong one...especially if running strong pumps and thick oil.

So motor is a gen 4 bored over .30 with full retro roller cam and lifters. 177 weiand and 950 Holley set at 7 psi.

Motor is out pulled oil pan everything looks to be where it should be. So I am stumped wondering if I should start tearing the motor down. The only thing I noticed is the oil lines from the filter from the cooler feel really soft and broken down.

I have know idea.

Steve oopoo:

Did you put a mechanical gauge on it first to verify 0 oil pressure?