0 oil pressure any ideas

[VitaBene]

We can shoehorn that Pontiac motor into that boat of yours, a little welding and a few homemade adapters and you will be good to go!! What is that- 455?

[Blue Thunder]

Bob,

I agree with some of the recent posts. I don't think you have the big problem that you think you do. What you are describing for oil pressure is right where my 1985 Liberator 5.7 Mercruiser was for years. After I gave it a "hot supper", the lifters would clatter a bit too. Those Mercruiser Chevy 350's with 4 bolt mains are nearly bulletproof if you take care of them and it sounds like you do. It's your boat, do what you want but I don't think you need to repower it. JMHO.

BT

[Sunset Bob]

Originally Posted by Blue Thunder

Bob,

I agree with some of the recent posts. I don't think you have the big problem that you think you do. What you are describing for oil pressure is right where my 1985 Liberator 5.7 Mercruiser was for years. After I gave it a "hot supper", the lifters would clatter a bit too. Those Mercruiser Chevy 350's with 4 bolt mains are nearly bulletproof if you take care of them and it sounds like you do. It's your boat, do what you want but I don't think you need to repower it. JMHO.

BT

Yes maybe I am a little to critical but its my nature.I am a FAA licensed aircraft mechanic.I am going to run the boat some more and see how it acts before I take out any guests.
And not like I want to spend the money but this boat will fly with a new Mag 350 OOOps there is that darn speed limit.

[VtSteve]

I had an 1994 Larson, small bowrider with the little puppy engine. Not sure I could have made it to the magical number. One thing to add. I have no idea if you've got an inclination to look around. But I've seen deals on new boats this year that really made me look seriously. My boat is an '06, so not great timing. But when I saw a pretty loaded Chap 250 cruiser going for $51 out the door? The used market is dead, even deader than the truck market. 2008 models are as cheap as new boats get.

[Winnipesaukee]

I'm what you call a "shadetree mechanic."

Here's what I think is going on.

In your crankcase, there is a spring-loaded piston that regulates oil pressure. Ideally, when the engine revs, this piston springs up, allowing the pressurized oil to bypass the "system" and redirect into/through the crankshaft, where it "seeps out" directly onto the crankshaft/conrod bearings. This action simultaneously regulates the oil pressure and lubricates these crucial bearings (keeping a film of oil between them and the crankshaft).

Every time you start your engine, these bearings wear a little more (get thinner) because there is no pressurized oil preventing them from touching (this is slightly different than "lubricating, where the parts actually touch"). Eventually, they wear so much that the space between the bearings and the crank grow so much that the oil "seeps" fast enough that the oil pump can't keep up.

This would fit your symptoms if the oil pressure relieve assembly (which I think Acres Per Second touched upon) or the spring was worn/damaged in a way that left it stuck open after running the engine for a period of time. This combined with the worn bearings would explain your problem.

One way to test it is to rev the engine (3000rpm) for a few seconds after the drop (do so at your own risk). If you get pressure again (pump is working harder at 3k than idle and may be able to overcome the extra volume loss), then I'm most likely right.

What can you do if that is the case? Run high viscosity oil. Viscous oil can't flow as fast and cannot "seep" past the crank bearings as fast. Try changing your oil with something like 20w-50 and that will extend the life of the engine a bit.

Oh, and get Seatow.

Hope that helps a bit. Best of luck. If you have any questions, post it up here or PM me.

[Sunset Bob]

Originally Posted by VitaBene

We can shoehorn that Pontiac motor into that boat of yours, a little welding and a few homemade adapters and you will be good to go!! What is that- 455?

Yep a 455 punched .030 (462) solid lifter cam allunium rods lots of porting to the heads trick oil system 11.1 to 1 compression about 600 hp pushed my 74 bird to 11:50s at 118mph not a bad ride in the 80s.but to much work it was like a second job

[trfour]

Originally Posted by Sunset Bob

Yep a 455 punched .030 (462) solid lifter cam allunium rods lots of porting to the heads trick oil system 11.1 to 1 compression about 600 hp pushed my 74 bird to 11:50s at 118mph not a bad ride in the 80s.but to much work it was like a second job

No wonder I like you! I ran a 58 Corvette back in the 60's, C/Gas and ran on the National record at New England Drag way, Sanford ME. 10.20000
Like you, when the fun came abruptly to a halt when they started bracket racing, kind of took all of the fun out of it. I had a 1959 F150 with a tricked 460 cu inch engine that we could have had fun racing. "LittleFoot' would scat too!
Terry

[Sunset Bob]

OK after running the boat this weekend and looking at new boats my old Larson is going to make the season.Sat I did a cruise around Long Island and today I took a cruise up to Moultonborough bay Poplar Island to see the eagles.The boat ran fine and as long as I don't look at the oil pressure gage I would never know it is a little low.I am getting about 25psi at 3000 rpm and about 6psi idle with no lifter noise.

[Just Sold]

Bob, If you now have the oil pressure you stated you should have nothing to worry about for this season. APS's suggestion of Mobil 1 and Slick 50 were excellent. Just keep and eye out to make sure the crankcase is full before each trip out on the lake. I also know that you never have beat on your boat so abuse was never a concern.

[macshpman]

I would have to say that if you ran that vette you must know some of the same racers I do. Doug Jounis must come right to the forefront as he also ran a corvette in that time frame. How about Phil Miller, Smiley Smullens, Ray Blake, Art Gallent, Bill Douglas and I am sure that you can name a few others. Also Sunset Bob you should a good oil in that engine that still has a high concentrate of Zinc and Phosporus. Brad Penn SAE 40 or SAE 50 would do the trick as you are more concerned with oil pressure and protection then gas mileage. You did mention that the oil pressure drops after a hard run which would suggest that it may be a temperature related problem. As oil increases in temp it thins and builds less pressure. Could it be an oil cooler that is losing its ability to cool the oil. That coupled with wear on the engine over the years could be causing the problem. Just a thought.

[robmac]

And don't forget Ron Keenan (Mr Boston TF) Billy Pike, Dick Ingalls oh the list is long. They all helped me get started, as well as Tony Grasso

[VitaBene]

Originally Posted by Sunset Bob

Yep a 455 punched .030 (462) solid lifter cam allunium rods lots of porting to the heads trick oil system 11.1 to 1 compression about 600 hp pushed my 74 bird to 11:50s at 118mph not a bad ride in the 80s.but to much work it was like a second job

I have a 70 Olds with a 455 punched to the same size. Did it up streetable with Mondello parts and pieces including adj valvetrain, had him port my cast heads. I need to git er dun