Oil Pressure Problems

[Matt89GT]

I bought this boat for 500.00 minus the leg, The engine is a gen 1, 350 cast between 68-79, It was rebuilt 3 summers ago used a couple times winterized and that winter someone stole the leg, upon cold start up it carries around 80lbs of pressure, after its warmed it drops to around 60 to 70 lbs. I run the boat up to around 3700 RPM's and the pressure starts dropping off to around 15 or 20 lbs. I can back off it down to 3000 RPMS or so and bam I have all my pressure back, I added a 6th qt of oil and the pressure doesnt drop off as fast, however I am scared of ruining a good running engine by aerating the oil. I dunno why they didn't use a stock chevy oil pump as I thought they was plenty well sufficient for a SB, It has a stock pan on it and I am thinking its sucking the pan dry, any reccomendations for a green horn boater?

 

[Haut Medoc]

Re: Oil Pressure Problems

I bought this boat for 500.00 minus the leg, The engine is a gen 1, 350 cast between 68-79, It was rebuilt 3 summers ago used a couple times winterized and that winter someone stole the leg, upon cold start up it carries around 80lbs of pressure, after its warmed it drops to around 60 to 70 lbs. I run the boat up to around 3700 RPM's and the pressure starts dropping off to around 15 or 20 lbs. I can back off it down to 3000 RPMS or so and bam I have all my pressure back, I added a 6th qt of oil and the pressure doesnt drop off as fast, however I am scared of ruining a good running engine by aerating the oil. I dunno why they didn't use a stock chevy oil pump as I thought they was plenty well sufficient for a SB, It has a stock pan on it and I am thinking its sucking the pan dry, any reccomendations for a green horn boater?

It sounds like the pressure relief valve is sticky.....
80# is high for a GM engine, anyway.......
I think you need to look at the pump, screen etc....
You will need to pull the engine for that, or at least the pan.....

 

[havasuboatman]

Re: Oil Pressure Problems

I agree. While it takes a hell of a lot more than 80 psi to blow apart and oil filter, your oil pump is quite capable or reaching it, and your discription indicates a sticking pressure release valve. Bubba is right. Just because your valve is releasing excess oil now at 80 psi doesn't mean it will continue to do so.
You are not sucking the oil pan dry unless you don't have enough oil in your pan to start with. (where would it go?)
If you have ruled out the sender and the gauge, your problem is in the oil pan.
If you haven't ruled them out, do so before you remove your engine.
Always rule out the easy stuff first. Replace the oil pressure sending unit first!

 

[Ridemywideglide]

Re: Oil Pressure Problems

I see a can of seafoam in your future. May just "unstick" that valve.. If not, your still tearing it apart.

Could also be the filter itself. Change it without adding oil to it to help offset the 6th quart.

 

[havasuboatman]

Re: Oil Pressure Problems

I had a ford currier pick up that literally blew the filter housing apart! It blew out the filter seal once on the P/O so he cranked the new filter on with a wrench. I got 50 feet from his driveway when I heard/felt a pop.
I was able to pull the pan without pulling the motor, pulled the oil pump out, took it apart and found nothing. I reassembled it and drove that thing for 100k more miles. Best $100 car I ever owned.

 

[Speakrdude]

Re: Oil Pressure Problems

I had that same problem on a 28' Bayliner with a 350 engine from circa 70's. With 5 quarts of new oil. Cold Idle 45-50 lbs, 3 or 4k rpms coming out of the hole, pressure would drop, lifters would ping. So I added another quart. Some people say those engines used 6 quarts, Ok, Same problem. While out experimenting one day, I disconnected the oil prs hose and drained out 2 quarts, keeping 4 quarts in the engine. PROBLEM SOLVED! No negative fluctuation in psi at all, at any rpm. Idle goes down, more rpm, goes up. Just like its supposed to. The problem turns out that for whatever reason, when the pan is tilted from the boat coming out of the hole, causes oil to get churned up in the crank shaft causing foam from detergent in oils. NOt sure if the problem is in the older pan design or what but 4 QUARTS from that point on. Solved. Hope this helps.

Jim

 

[ENSIGN]

Re: Oil Pressure Problems

Check the oil pressure with a mechanical gauge. Your sender or gauge may not be accurate or may not be matched.

 

[Gary H NC]

Re: Oil Pressure Problems

I would change the oil and filter....be sure to get the correct amount of oil in.
You stated you added an extra quart?
Run plain old SAE 30 weight.

Take out the electric oil sender and get a mechanical gauge and re-test..

Yep.easy stuff first.....the electric sender gauges can be really flaky...

 

[havasuboatman]

Re: Oil Pressure Problems

I had that same problem on a 28' Bayliner with a 350 engine from circa 70's. With 5 quarts of new oil. Cold Idle 45-50 lbs, 3 or 4k rpms coming out of the hole, pressure would drop, lifters would ping. So I added another quart. Some people say those engines used 6 quarts, Ok, Same problem. While out experimenting one day, I disconnected the oil prs hose and drained out 2 quarts, keeping 4 quarts in the engine. PROBLEM SOLVED! No negative fluctuation in psi at all, at any rpm. Idle goes down, more rpm, goes up. Just like its supposed to. The problem turns out that for whatever reason, when the pan is tilted from the boat coming out of the hole, causes oil to get churned up in the crank shaft causing foam from detergent in oils. NOt sure if the problem is in the older pan design or what but 4 QUARTS from that point on. Solved. Hope this helps.

Jim

You hit 3 to 4 thousand rpms coming out of the hole? I have a bayliner Capri ($800) When I firewall the throttle I travel about 30 feet and I am on plane and before I hit 2k. That's with a 305 and a cobra (and just me in the boat) That little POS practially jumps out of the water. It's ugly, no windshield, dinged and scratched, and been in a movie. Piranah 3D.

 

[Speakrdude]

Re: Oil Pressure Problems

6000 lb of boat, single 350.

 

[havasuboatman]

Re: Oil Pressure Problems

6000 lb of boat, single 350.

I'm an idiot, I read 18 ft. boat. Don't ask me how.