Re: how to check compression?
Compression should be around 125 on each cylinder. You should do it on a warm motor instead of a cold one. One of our previous members was The Marine Doctor and he mentioned that WOT really has no effect on the end results on an outboard so dont go to the trouble of bypassing the neutral interlock switch. Make sure them plugs are grounded like mentioned above. You could see compression numbers from 100 to 150 depending on the motor and the tester. Either is all right as long as each cylinder is within say 10 % of the other cylinders. Also on compression testers. I bought one at sears that had some kind of extension on it that if you have it hooked up you will damage the piston. Verify how close the piston comes to the opening by inserting a pencil or pen into a cylinder and turn the flywheel clockwise (make sure plugs are all out and or battery is disconnected for safety reasons) till the pencil is as far out of the cylinder as possible This is Top Dead Center. You want to make sure that when the compression tester is screwed in it does not go deeper than that depth.
