Erratic tach

[gotaf7]

1B914695 2012 150 Optimax, my tach on occasion goes crazy will bounce around and seems to read about 1000rpm to high, after a while it settles down and seems normal. Any ideas where to start with this?

[SilverFox579]

On back of tach, note the current switch position, then carefully sweep switch back and forth being careful to not exceed mechanical limits, return switch to original position. Contacts will sometimes develop a small amount of corrosion and sweeping the switch "wipes" them clean and restores normal function.

[gotaf7]

Thanks I will try that.