Its not likely you have too much compression unless the motor has been
modified or incorrect parts have been installed. The way to check the
compression is with a compression gauge. Expect it to be between 65
& 75 Lbs. You should remove both spark-plugs and turn the motor
over. It should be more than “fairly free moving” with out any binding.
If it is free and smooth check the spark plugs for any sign they are
hitting the pistons. Not likely but check for it anyway.
If you find it is binding when rotating the flywheel that could be
anywhere, including the gear case.
Tubs.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.