6.2 MPI cylinder compression check numbers

[GJarrett]

I am sea trialing a 2002 260 Sundancer tomorrow and got the mechanical survey results back. Engine has 665 hours and all cylinders except for #5 read 160-170 which I am completely comfortable with. #5 reads 145, is that anything to be concerned about?

 

[KevinC]

It's in range (Minimum compression recorded in any one cylinder should not be less than 70% of the highest recorded cylinder.) But raises the question about why?

Was the engine warm or just coming off storage?

More info here:
https://www.perfprotech.com/blog/bo...s/mercruiser-gasoline-engine-compression-test

-Kevin

 

[scoflaw]

Probably will need a valve job in the near future, but will be OK for a while. Do a leak-down on that cylinder. Can use the results to negotiate

 

[Wanderer 290]

When a leak down is done follow it with a leak down after injecting a small amount of oil into the cylinder. This will indicate whether it is the rings / cylinder or valves are bad.

 

[GJarrett]

Thanks for the suggestions I had not thought of doing a leakdown on that cylinder. I did the sea trial, negotiated the price down $4k, and bought the boat. With full fuel, water, three people on board, and slightly rough seas she almost jumped on plane and did WOT 4800 rpm with 22p props. I think book WOT is 4800 ~ 5200 so I'm satisfied. I'll do a leakdown at first service and see what it does.

 

[aerobat77]

if she sounds , feels and runs well i would just go boating !

 

[cfd95]

#5 is one of the center cylinders which are right below the risers.
#3/5 and 4/6.
These are typically the cylinders you lose when a riser or riser gasket fails.
IE: Broken valve or pitted valve seats from water intrusion.

 

[GJarrett]

Thanks for the input, I did not think of that