Compression numbers

[b_lish1966]

I checked the compression on my 1987 70hp johnson and this is what is read, 1 and 2 cylinders 125 psi each, number 3 cylinder 115 psi. My question is should I be concerned about the 10 psi drop on number 3. The spark is also good.

 

[Dhadley]

Re: Compression numbers

I'd try a decarb and recheck. If you're concerned, pull the head or get a bore scope. You're within the tolerance but it is worth a decarb.

 

[b_lish1966]

Re: Compression numbers

What's a decarb?

 

[jtexas]

Re: Compression numbers

clean the carbon deposits out of your engine.

click over to the engine FAQ section of iboats, there's a thread on why & how to decarb.

it's what I'd do - can't hurt, might help.