[Boatguy]

My suspicion would be that there’s an electronics problem. Or a wiring problem. That’s the easiest to diagnose.

I damaged my gauge cluster and have had it completely apart. The tachometer needle is run by a circuit board under that. It’s all one piece. You can replace the whole thing if you think that’s what’s faulty, but I would start looking at the wires that go between the gauge cluster and everywhere else that they run to. I’m not sure where the pick up is for the tachometer, but the wire between the gauge cluster and that pick up is probably your best bet. Check to see if it hasn’t grounded out or worn through somewhere.

There is a wiring diagram in the manual that is pretty good.