Can anybody tell me what the compression should be on a 85 Johnson 150 outboard motor be? thank you?

Question

Can anybody tell me what the compression should be on a 85 Johnson 150 outboard motor be? thank you?

Answer 1

Engines of that age are usually between 115 and 125 lbs.  but they should all be about the same or with in 10-12 lbs. of each other.  If one is like 70 lbs.  remove the head on that side.  If the piston has failed, you'll know right away.  I don't think I would invest in repairing the power head.   Often it's #3 that's bad.  But it's the damage to the crank that kills a lot of these engines.  Good Luck!!!!!

Answer 2

Difference between cylinders is more important that actual numbers.

You want the lowest to be within 5 to 7% of the highest.

Anything upwards of 100 would be considered acceptable by most.