I have a 1973 Johnson 65hp outboard. A few weeks ago I tried to start it for the first time in about 18 months. The engine won't turn over. I have removed the plugs and have been applying penetrating oil in the cylinders. I put a breaker bar on the nut over the flywheel thinking I should be able to break it loose, but no luck. Any ideas on what to try next. All ideas appreciated.