Opinion on Compression

[Graham Ridley]

I have a 1985 Sea Ray 260 it has a 5.7 liter engine. I have just run a compression test and have the following results:
DRY WET
1) 142 209
2) 126 205
3) 180 224
4) 185 215
5) 125 170
6) 105 160
7) 185 208
8) 120 180

Should I be concerned or replace the rings? Suggestions and opinions welcome.

 

[scoflaw]

I'd be concerned. How's it run ? How much oil does it use ? Can you live with it ? I'd pull that out in a heart beat if it was mine, but that's me.

 

[fwebster]

We see this a lot on the Gulf coast where boats have been stored over the winter. When not running, several intake and exhaust valves are open and sometimes surface rust forms on the valve face. Before I did anything or spent any money, I'd run the boat for several hours at a decent or planing speed and then retest the compression. You might be lucky and find that the valves clean up and the problem will go away.

 

[Air O'Nautical]

From experience, I completely agree with Frank.
Those numbers are currently not acceptable!


Boats that aren't run often, are subject to rusty valves that affect sealing and therefore compression. This is why we here in the North fog our GAS engines with oil during winter lay-up (Diesel engines are already full of oil).
It's rarely the bottom of the engine that's the problem, piston/rings ect.
A top end job is a common procedure.

 

[scoflaw]

The wet test has been used as a benchmark to check ring condition. It would be unreasonable to think the oil came up off the piston and sealed both intake and exhaust valves to the degree that was observed in his wet/ dry results.

Totally agree with running it and retesting. Leak down test would give more insight to where the lost compression is going

 

[Bt Doctur]

Those reading are do not correspond to a 32 year old engine. see post 4