Wacky Tach

[ARoss]

We were running back from Ocracoke the other day, cruising @ about 7 kts, 1950 rpm, when without any change in the throttle or engine pitch the tach on the upper helm jumped up to ~2400 rpm, and stayed there. A quick check of the lower helm show it was still reading 1950-2000 rpm.

Any ideas where I might start looking for a reason this might have happened?

FL 120, single.

 

[skipperdude]

I would first check the connections.
Is it the same sender for both tacs?
Is the tac run off the alternator or engine?

SD

 

[ben2go]

Yep.We need to know what drives the tach.Then we can get down to diagnostics.