Tach not reading correctly

[Captain78]

I have a '97 175 Bow Rider with the Merc 3.0L engine. When everything is shut down the tach reads 2000 RPM. At Idle speed the tach reads about 4000 RPM. At WOT 42MPH the tach is burried. Any ideas what the problem is?

 

[Prater]

Have you cleaned the terminals? I dont really think that is the problem but never hurts on a tach. Sounds like the servo gear went bad.

 

[boatmailster]

I have a '97 175 Bow Rider with the Merc 3.0L engine. When everything is shut down the tach reads 2000 RPM. At Idle speed the tach reads about 4000 RPM. At WOT 42MPH the tach is burried. Any ideas what the problem is?

discussed here before, search threads. if incorrect reading then most likely corrosion on calibration screw, but if it stays on with battery switch off then looks like needle moved on shaft (or shaft itself) and not returning to "0", and need mechanical repair (may moved after you jumped a wave and had a hard landing)