1992 Johnson 200GT. When I purchased the boat this last spring, noticed that tach was erratic. Initial investigation showed burnt ground wiring from key switch to tach. Found loose main ground at starter and tightened. and replaced burnt wiring. Tach still erratic and finally quits alltogether. Read Joe Reeves tach test and tach does not work on yellow/grey or yellow, so I think bad tach. Decide to check charging before I purchase parts, and lo and behold rectifier/regulator shows bad. Do I need to replace both tach and rectifier, or replace rectifier and recheck tach?
