[Glock2710]

I am looking at buying a boat with a 1997 80hp yamaha. The compression check is 101-100-99 top to bottom. Should I have any concerns with these numbers being slightly low? They are all close so that is pretty good but I thought I would ask here from some with more knowledge than me.

 

[Brett]

Less than 2% compression difference between high and low cylinders is good.
The values you read may be affected by the gauge. I have one compression gauge
that reads consistently 10-12 psi lower than my other two. I expect to read 110 psi
on an older motor. Anything above 110 is gravy. 

btw, if I get a sub 100 psi reading, it usually means
I forgot to make sure the intake was wide open, before testing. :-[ ;D

 

[Capt Dan Medina]

I've got a 96 75 HP yam I... compression is the same... runs great...