OMC used a few different Ignition Systems on that lineage of Motor. The Low Tension System used on the 76 model is quite Reliable and easy to service, and Service Parts are easy to attain. Those neat Electronic Boxes on later Motors, are not serviceable and require replacement when they fail, and as most owners will agree, Not Cheap.
Along a similar path the early 9.9/15hp motors used points. By 1977 these were Breakerless CD. By the 90s owners of these engine were asking if they could convert them to Points Ignitions for the Reason mentioned