Offshoreonly.com - Engine Rebuild -- What's Actually Involved

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How do can you do a leak down if there's no compression in the cylinder, or did I miss something.

The leak down will isolate where the problem is resulting in the loss of compression. The air will escape either thru the intake, exhaust, or crankcase.

I understand how it works, but if there's NO compression you cant tell anything, could be a hole in the top of the piston, the OP said no compression not low

Quote:

Originally Posted by 33outlawsst (Post 4454154)

I understand how it works, but if there's NO compression you cant tell anything, could be a hole in the top of the piston, the OP said no compression not low

If there is a hole in the piston you will hear the air escaping from the crankcase (breather), instead of out the exhaust or through the carb if there were a stuck/broken valve. It might not tell you for certain that it is a hole in the piston versus a broken ring, but it would help to isolate the problem a little more and maybe tell you if the engine has to come out versus possibly pulling a head and fixing a valve.

Quote:

Originally Posted by jfried (Post 4454115)

Yeah -- the marina is doing that this afternoon... why they didn't do that as soon as they found out the compression was gone -- I'm not sure.

Doing some reading, seems like I'm hoping for something in the top end of the motor.

While I'm certainly in no position to debate this assesment (and fear it may be accurate), it does seem a bit strange to me. Even after the overheat, the boat was running absolutely fine, except with more than 3/4 throttle.

I had a chunk come off of the ringland of #6 and it busted off a 1/8" piece from the intake valve. Boat ran fine from idle up until about 3800 RPM. If you tried to lean on it, it would backfire through the carb. I originally thought I had a weak fuel pump causing a lean pop, or an ignition issue. Only after a compression test showed about 80 PSI in #6 did I realize I had a major issue. When I pulled it apart I found a chunk our of piston #5 as well. Compression was fine in that cyl.

If you are truly getting zero compression it almost has to be a really big hole in a piston or valve.

I would guess warped head and blown gasket.

I think my heads warped for posting on here

Let us know please, the final verdict

What's actually involved? Money. Lots of money....

Quote:

Originally Posted by jfried (Post 4454115)

i am not sure how an engine can run fine when it has a dead cylinder.