I have a 1962 johnson 40 hp w/ electric shift(2-stroke). I know nothing about motors. with some help, I cleaned up the starter and rebuild the carburator. If the plugs are out, the flywheel with turn fairly easy with the starter or the pull start. But when the plugs are in, it will only turn once with the pull start and its very difficult, won't turn at all with the starter. I figured maybe the exhaust ports were clogged but when I removed the exhaust cover, and had a view right into the cylinders, it did the same thing. any suggestions?