Compression on a 1977 140hp V4 johnson?

[lake_time]

I know you need to have equal compression across the cylinders but what SHOULD it be on this motor? Mine is <br />Cly 1 103-PSI<br />Cly 2 101-PSI<br />Cly 3 103-PSI<br />Cly 4 100-PSI<br />Even my math says this is a 3% variance and I keep hearing 10% is OK but any idea what it would have been from the factory? Can you gauge the wear on a motor by the drop in compression?<br />Thanks as always.. Dave

 

[JB]

Re: Compression on a 1977 140hp V4 johnson?

On an OMC V4 in top shape expect 125 plus or minus 5 lb or so. Their book says a variance of 15 lb is okay. They also say that 100 is the minimum. Sounds like your cylinders are equally worn and nearing the time for overhaul. Happy Boating!

<br />JB

 

[lake_time]

Re: Compression on a 1977 140hp V4 johnson?

Thanks for the info JB... I'll rebuild sometone next year myself.. I have lots of time... but not money..Could I just used over sized piston rings or go for a re-bore?<br /><br />Dave