'66 OMC 9.5 compression 75 & 75 - OK??

[ledgefinder]

Just picked up a nice 9.5 Johnson fishing motor, 1966. The compression is dead even cylinder to cylinder (75 & 75), but still that seems low. Does anyone have definite knowledge that this is OK? It's not the gauge - it's a good gauge and I am getting 120-135s out of mid-70s OMC V4s. (Maybe they ran lower compression ratio on these smaller old motors?) I tested a mid-80s 9.9 OMC that read out at 90 and 95. Thanks!

 

[JB]

Re: '66 OMC 9.5 compression 75 & 75 - OK??

Howdy, Finder.<br /><br />I agree that 75 seems low, but clearly neither cylinder is toast.<br /><br />You might improve it with a serious decarbonizing.<br /><br />I think you need an on-the-water trial.