G3 analog tach reading high

[Elkins45]

I have a 2006 Yamaha F50 2 stroke on a G3 V167 with analog gauges. I’ve owned this boat for four years now and out of nowhere it’s started reading around 800-1000 rpm high at WOT, proportionally less at lower revs. Normal idle at what sounds like around 1000 is reading 1200-1600 over the course of a day. The tach is part of an analog gauge cluster, not the Yamaha digital unit I find in most posts when I Google this issue.

Any suggestions on where to start tracking down this issue? I have a digital tach/hour meter I bought but never installed I’m going to mount before my next outing to verify true rpm, but if there’s an easy fix I would like to try that as well.

 

[Sea Rider]

Install the induction tach and contrast it against the faulty tach readings. Clean all tach's electrical contacts, but usually once kaput and done must buy a new one, preferably buy an OEM.

Happy Boating​

 

[99yam40]

I would flip the switches that set the tach for the proper motor it is attached to.
could be there is a bad connection in those connections inside the tach.
flipping them back and forth may help

 

[Faztbullet]

Could be erratic rectifier also...