compression test

[cdbaum]

hi,i have a 1991 evinrude 115hp 4cyl 2-stroke,just wondering what the compression should be on the cylinders? motor cold and a crappy testing gauge i got 85 83 83 and 80 psi...does this sound close? and should i start and warm the engine before the comp test?

thank you

 

[dehydrated]

Re: compression test

throttle wide open, good batt charge should be about 90 differant gauges but should be ok at least your fairly consistant

 

[Rick.]

Re: compression test

The engine should be warmed up to operating temp. and all plugs out when testing comp.. Not sure if the numbers are good or not. Best of luck. Rick.

 

[cdbaum]

Re: compression test

ok found the info for the proceedure...just need to know what is a good comp press for this motor

thanks for the help

 

[tashasdaddy]

Re: compression test

i never warm a motor to compression test it, and on a 2 stroke no need for idle to be wide open.

i would like to see atleast 100 depending on tester, borrow one and test again. it sure sounds like the motor need a through Decarb, with seafoam, or BRP Engine Tuner.

Decarb

i would do a decarb, then if it did not come up, the head gasket.
Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck
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[JB]

Re: compression test

Your numbers are fine, CDB. They vary by less than 10%. There are a hundred reasons for the psi to be less than some artificially generated spec, and none of them matter if all 4 give the same reading +/- 10%.

You might run a decarb and try again. You might try a different guage or warm the engine up first. Your new readings will be different, but not necessarily better.