150 Tach Problems

[Redpower]

I was on the water yesterday, everything was fine until I was ready to bring it out of the water and I noticed that the tach over 4000 rpm was bouncing erratically. No change in sound on engine. Guage? Tach cable? Tach drive? Any way of testing? Thanks in advance.

[boats.net]

Check the wire connections (loose or corroded), if ok then the tach is probably bad.