For 1976 model year wiring, it seems strange that he cut the tach wire and, I am assuming, he also stopped the cylinder misfire? There is seemingly no connection between the two, unless somewhere in the box or harness, there was a short between the stop circuit and the tach circuit. I am pretty sure that year had an alternator driven (common type) tach and not an ignition-driven one. I gotta go look at a diagram, now….
Now if, like many Merc owners, his engine is about ten years older than he thinks, that’s a different story.
Long live American manufacturing!
