compression for dummies

[Mark Overfelt]

what is the proper way to check compression on a mariner 3cyl 70 hp motor, and what should the readings be?

 

[aeronutt29]

Re: compression for dummies

First, do a search on this forum for "compression" and spend some time reading.<br /><br />Second, take the reading with all the spark plugs removed and the throttle wide open. Crank the motor for 5 seconds for each reading. It's much more important that the readings be within about 10-15 PSI of each other than to be within a certain range.

 

[norman158]

Re: compression for dummies

also motor needs to be warm

 

[letsbarbq]

Re: compression for dummies

yes that is right. Run the engine first for a minute. Then test it on the second time. I did a compression test on an engine that was ran for awhile. it had 90 psi. I serviced it and decarbed the engine now its a whopping 115-120. big difference.