Good compression on 8, High leakdown on 1 cyl
 

Looking at a boat with twin 502s. Approx 125 hours since last refreshed.

Compression numbers all in the 150-180 range.

One cyl on each motor is showing up at 65% Leakdown, which seems super high to me. The shop doing the testing says it could be due to being winterized, maybe a little rust on a valve preventing full seating, etc but I'm skeptical about it being one cylinder on each motor like that.

Walk away? Renegotiate? Other?

That can happen but yes seems odd one cylinder on each??? Not ideal way to ck under current conditions. How many hours total on engines and who did the REFRESH? What all falls under refresh? Any receipts? And who performed the work?

Does the boat and engine bay look meticulously maintained?

just some things I’d take in consideration.

They should be able to determine where the leakage is coming from. A true 65% would mean it needs to be torn down.
What % are the other cylinders??

His feeling was the leakage was top end because the compression was pretty good across the board. Shop has a good reputation (Boat Doctors of Gilbert SC).
Not sure what the other leakdown numbers were but I can find out.

Sidetrack: 180 psi ? How much static compression do these motors have ?

Sometimes leakdown will be bad on a few cylinders when engines haven’t been run. Did they listen to where air us escaping ?

Enough compression that the current owner runs 93 octane. Not sure of exact comp ratio.

I don't know if he heard where air was escaping but I did ask whether he thought it was top end or bottom end, and he felt pretty confident that it was top end, with the caveat that he can't be completely sure without a teardown.

An ear to the intake or the exhaust will tell you if its heads, same ear to oil fill cap will tell you if its bottom end

Other cylinders were between 5-15% leakdown.

When doing a leak down you always listen to where the air is leaking, WTH.

As a example that is a LOT more leakage then I have on my 680 hour HP500EFI's that were done cold. As a matter of fact when we did them they had not ran for months. Just to give you a comparison. It should be looked into a bit more.

I am also with SB 180 psi is up there. Don't forget around us on the water all you can get is 90, needing 93 will make a lot of our runs a PITA. Better be to the top for a Sebastian run and play.

WG, I know, I was thinking the same thing. I might take a pass on this one.