Mercruiser 140 3.0. Compression question

[Jjthejetplane]

I just bought an old Larson 16' I/o with a 140 mercruiser. The boat was full of water so I'm repairing foam and redoing the stringers etc. The engine seemed to be ok. I checked compression and got some scary figures.
#1 cyl = 90 psi
#2 cyl = 125 psi
#3 cyl = 130 psi
#4 cyl = 105 psi

My question is, will the boat run ok like this?
Now these are cold engine figures and know that comp goes up when the engine is warm.

I'll appreciate any info I can get. This is my first boat and first boat project. Having fun with it so far except tearing out all the water logged foam!!:-( that sucked.

Thanks JJ

 

[Don S]

Re: Mercruiser 140 3.0. Compression question

It's not going to run good with that compression. When you say cold engine, how cold, not so much temp but time. Was it cold by one day since running, or by months/years?

 

[Jjthejetplane]

Re: Mercruiser 140 3.0. Compression question

It hasn't been ran in years

 

[Don S]

Re: Mercruiser 140 3.0. Compression question

It hasn't been ran in years

Then those are meaningless numbers.
Get it started, even if for only 15 to 30 seconds, those number will likely change.

 

[Jjthejetplane]

Re: Mercruiser 140 3.0. Compression question

Cool, thanks. Hopefully they get better and not worse. I won't be able to tell for a while. Gotta get a new ignition coil.