[THEFERMANATOR]

Originally Posted by Larryrsf

My factory-trained mechanic said the compression numbers should be within a few pounds of each other-- which is more important than the number itself. He declared my old Evinrude 150 in "new" or recently overhauled internal condition with compression just over 100# in ALL 6 Cylinders. If one had been several pounds lower, that would have indicated problems with rings or valves, etc.

Larry

Ideally you want all cylinders within 5% of each other, but 10% is considered accepteable. You also want to make sure they are within a certain range though as I have seen engines wore slam slap out have compression with 2% of each cylinder, but were shot internally. Had a V4 with all cylinders at 60, but a good engine like it should have been at 115-120. Turns out it had standard pistons in a .020 bore engine. When I finally got it to run, it rattled like a metal can filled with rocks.