So. I found the problem today. There is a coaxial wire that runs to the right rear mag, actually goes to each of the mags. However the ground wire was broken off from the crimp connector. I replaced and now tach is solid. My guess is it was also hurt overall performance of the engine.
When checking out the wires there was also a ground strap to the rear alternator that needs to be replaced. I had no primary wire but will do this soon as well.
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