Your engine should have a compression release mechanism on it. It usually rides in a track on your manual starter, and moves a lever left and right to operate poppit valves that are on the cylinder head. This unit only operates while starting the engine, and releases the compression, making it easier to start. Check your engine and see if it has this item. If it does, check its operation to see if it is operating properly and actually opening the little poppit valves. If you have any questions, PM me. I have been working on OMC products for around 30 years, and will give you all the help I can via email.