I recently purchased a 57 Sea King 5 hp. It wasn't running. I cleaned the carb. and fuel filter, new fuel line, replaced the plug wires, plugs, coils and points. Set the point gap at .020, Runs great for about 10-15 min. then slowly dies and won't start back up. Let it sit for a day and it fires right up runs great for about 15 min. then same thing. Compression test shows 60 lbs on both cylinders. Any other ideas as to what may be causing this?