1982 90 HP Mercury, 6 cyl, engine overheating, compression test

dmixon · #1 July 24th, 2003, 03:52 PM

I've noticed on many other posts concerning engine overheating, a compression test of each cylinder is recommended to find out if any internal damage has occurred. My manual on this engine does not document a compression test so I looked up compression testing in my "Stockel auto service and repair manual". This manual recommends cranking the engine and letting it warm up until normal operating temp is reached. Then it states that you should "block the throttle valve wide open and the choke must also be fully open" before proceeding with the compression check. Would this also be the recommended steps on this Mercury engine?

Yepblaze · #2 July 24th, 2003, 04:15 PM

If you desire, you can do it that way.

But, I believe that on your motor the carb butterflies have a large idle notch cutaway in them so as to not have much, if any bearing on test, weather open or closed.

And to the temperature, from what I've found is a warmed motor will produce higher readings, yet what is most important is a variance between individual cylinders not more than 15% be they taken warm or cold.