compression on merc

[RIDEPATE]

ive got a 72 650 what would be a respectable psi on this thing 80 to 125??and how much diffrenetial in psi between cylinders is acceptable?? thanks jim

 

[JB]

Re: compression on merc

Howdy, Ridepate. You need over 100# and less than 15# difference between high and low to say compression is good. Many engines that, um, "mature" continue to run well and deliver satisfactory service without meeting those numbers.<br /><br />Are you seeking an answer to a problem, or simply reassurance that your old thumper is in good health?<br /><br />Red sky at night.<br />JB

 

[RIDEPATE]

Re: compression on merc

j.b thanks for the reply,i'm just tinkering with this new (to me)motor,i havent checked it yet,so was just asking so i'll know what i'm looking at.i don't suspect any problems as the old girl purrs like a kitten, but it (the boat)has some performance issues(planeing.top-end) thta i want to improve on and if compression is low or marginal i w'ont bother.thanks jim