compression hot/cold

[mckee1787]

What differences in compression should I expect between a hot and cold motor? I have a 1987 90hp evinrude model # e90tlcur. I measured 95psi on all cylinders when cold.

Thanks

 

[tashasdaddy]

Re: compression hot/cold

did you follow this?
http://forums.iboats.com/showthread.php?t=313963&highlight=compression
guages are different, your reading on my guage would be a little low. a decarb may do wonders for it.

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

 

[mckee1787]

Re: compression hot/cold

The gauge that I have is an inexpensive $20 harborfreight model. I haven't done a decarb, but just wanted to know what compression increases percentage wise if any would a warm engine produce versus a cold one.

Thanks

 

[tashasdaddy]

Re: compression hot/cold

not enough to matter. i usually do cold compression test. do the decarb.

 

[mckee1787]

Re: compression hot/cold

Thanks, will do.