Logo
FULL SITE MENU

Compression Test

I

iwannafish55

New member
When performing a compression test on an outboard motor, does the lower unit (water intake) need to be submerged in water or it can be done out of water

I know to best perform the test, the motor needs to be running first but I don't have water access....the boat I want to buy is at a storage location...just want to do a cold comp test

thanks
 
We compression check engines all the time that don't and haven't ran in decades. Just remove the spark plug on the cylinder you want to check, screw your guage into the spark plug hole, and pull the starter rope. If it's electric start and the starter is good....hook up a battery and hit the starter. Never heard of the engine having to be running for a compression check, and I'm not sure what flyingscott is talking about. He is right about the fact that you ALWAYS want to rebuild the water pump, but that has nothing to do with a compression check. Unless I'm just reading the posts wrong.
 
I believe the question is does it hurt the pump to crank it over dry to do the compression test. The answer is Maybe. Or Maybe not. But it is moot anyway, since you are going to replace it.
 
Back
Top