Originally Posted by SWGA Boater
Ran the boat with the engine cover off this afternoon. Have isolated the oil leak to blow by out of the dipstick tube. Almost immediately after getting into the throttle dipstck pops up and starts spitting oil out. Had previously installed a new pcv valve and a breather oil fill cap. So much pressure was coming out of the breather cap it literally looked like smoke. Put my nonvented oil fill cap back on which leads to more blow by/oil coming from the dipstick tube. Should have taken a video...
I'll try and pick up or rent a compression gage tomorrow. Piston ring blow by is the only thing I can think of causing this much pressure. Seems to idle fine and no skipping under a load though.
Any other thoughts?
Remove the oil filler cap and the breather cap and remove the raw water pump so you can rotate the crank manually. Make sure to disconnect the battery first- don't want any possibility of it starting. Listen for what sounds like gasping coming from the oil filler openings. If you do, it could indicate blow-by.
Rather than do a compression test, do a cylinder leakdown test. It could be rings, but it could be scoring in one or more cylinders, too.