Marine: Boating, Sailing, PWC, GPS and Navigation - Cylinder compression #'s?

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jonny
10-23-05, 06:09 PM
1987 Johnson 175hp. V-6 Outboard. 2 stroke
What are the compression #'s for one of these motors new?
Now, being it's an '87 with many hours on it obviously the #'s won't be as good as new.
I warmed up the motor and did a compression test on each cylinder. I didn't add oil and do a 2nd test to check rings or anything.
5 cylinders are equal in compression.
1 cyl. is roughly 60% of the other 5.
Anyone have any answers?

I would like to know what a "good" number should/would be?
TIA
jonny

robby521
10-23-05, 10:59 PM
Minimum compression of 100 lb in each cylinder. I would feel better with 125 lb. Balance between the cylinders also important. More than 10-15 lb difference between cylinders is not good.
jonny
10-24-05, 07:26 AM
Minimum compression of 100 lb in each cylinder. I would feel better with 125 lb. Balance between the cylinders also important. More than 10-15 lb difference between cylinders is not good.

Thanks Robby,
That's what I was afraid to hear. :(

jonny
11-03-05, 05:37 AM
An outboard expert told me yesterday that re-ringing outbards is useless. He says, rebore & new pistons @ $4K.
It this true?
robby521
11-03-05, 06:35 AM
if there is alot difference yes it will be useless.if you can get it all down at that price,that is good.when done follow brake in and it will be better than new.a new one will run between 8k and 11k