What is good compression for '87 70HP Merc?

[chiguy]

I'm looking at an older Merc tonight. What should I read for compression for good cylinders? Again, it is a 1987 70HP. Thanks.

 

[JB]

Re: What is good compression for '87 70HP Merc?

All cylinders shouold read within 10% of each other.

A proper procedure with a good guage should give 100psi or more.

 

[chiguy]

Re: What is good compression for '87 70HP Merc?

Thanks, JB. I've seen good compression expressed as 145-145-140psi and as 120-120-120psi. The 10% factor I take accounts for scoring of the cylinder wall of excessive ring wear on one or more cylinders. Thanks for the tip of looking for 100psi or better on an older motor.
Chiguy