I recently purchased a boat with a 1998 Johnson 50 hp 2 cyl. 2 stroke outboard. The system check tach needle was stuck on 1100 rpm and inop. The charging system was also inop. I checked and found rectifier had open continuity. Upon replacing rectifier I found that at 2000 rpm I got intermittent spikes of charging output. I had not replaced the tach yet, so I disconnected the gray wire from the rectifier. ( I assume it goes to the tach). When I did this the charging was normal. Now I dont know if the tach being bad caused the old rectifier to go bad or just coincidence, but be aware that the tach can affect the charging output of rectifier. 8)
