Re: How to check timing on 1980 50hp Mercury
One other thought for you, get a dial indicator from Harbor Freight and drill out the ceramic from an old spark plug and make a tool to check top dead center of the #1 or top piston. When you get the top piston at top dead center rotating the flywheel clockwise, make sure the timing pointer is actually aligned with the flywheel markings for TDC.
Good luck and great motors!