Compression?

[Thuggin4Life]

Any one know what good compression for an outboard is? I can't find much info using google. I read 140-160 is good for a car. And I know you want the comp to be close from one cylinder to the next. I have a 1990 evinrude 6hp 2 stroke that comps really close to 90. I bought a early 90's merc 9.9 2 stroke and comps at 100 before and after trying the wd-40 trick. both motors have even comp. someone told me that 100 comp is low for a 2 cycle motor. I called clemens marina today and they said 100-110 is good for a small outboard. Can't seem to find any factory specs on compression and really have no clue just gave myself a crash course on compression today. Please anyone with knowledge on this subject let me know.

 

[Bifflefan]

Re: Compression?

100-120 is great, 90 to 100 good, As long as they are with in 10-15% of each then you are fine even if they are lower.

 

[JB]

Re: Compression?

A rope start 6HP? Anything over about 60psi.

 

[Thuggin4Life]

Re: Compression?

both motors rope start.

 

[lindy46]

Re: Compression?

Compression varies greatly depending on the gauge you are using, the temperature of the engine, whether pull start or electric start, and on the pull start, the number of pulls. Guess that's why there is no specification for compression. If you're getting 90-100psi with less than 10% variation on a small pull start motor, you are in great shape.