GNJ

Refreshed both motors over the winter - top ends done on both motors.
Mobil 15-50w oil
Mobil 1 oil filters
Port engine oil pressure gauge reading 60psi at idle, starboard reading 40psi at idle. Launched boat and ran at 3300-3500 rpm for about 5-10 mins. Powered up to 4500 - 4700 rpm and then smelled oil. Gauge on port motor was pegged at 80psi! Other motor normal at 50psi. Stopped, open hatch, saw about 4 ounces of oil had spewed out of diptick tube all over front of engine.

The only thing I can think of right now is changing the oil filter bypass valve in the block (GM 25161284) I ruined the old one taking it out.

Anybody have any thoughts?

Bajajay98

Sounds like you have some crank pressure coming from somewhere in the motor that's cause it to puke.

snapmorgan

iTrader: (2)

It is not an oil pressure problem, It is a crankcase pressure problem. Might just be because the rings aren't seated yet. Possible broken ring or the crankcase not properly vented.

jeff32

compression checked?

mike tkach

iTrader: (3)

or maybe detonation bad enough to damage the ring lands.

articfriends

iTrader: (1)

Bad injector melted a piston already? Usually something like that when you have severe blowby

SB

iTrader: (1)

Just to make sure on the same page, last fall you indicated you only had 80hrs on the motors. Why the rebuilds again ? IE: What happened ?

For those who didn't see or remember this (like me) here is a thread he posted last fall with driveability issues and what performance parts are in these motors:
http://www.offshoreonly.com/forums/g...0efi-help.html

GNJ

SB - Headers leaked and heads had to be refreshed.

GNJ

Jeff32 - 120-125 on all 8. Leak down all around 10%

Unlimited jd

iTrader: (5)

Is that cold? Sounds a little low for 500's