Flybridge Tachometer reading high

[bowersmichael]

I have an '86 Sedan Bridge 300 with twin 350 Mercs. The port engine has started to read higher RPM on the flybridge than it shows in the cabin at the lower helm. When I look at the cabin gauges, the port and starboard read similar values when applying the same amount of throttle, but they are off by about 500-1000 RPM on the flybridge. We just had the engine serviced and the transmission rebuilt, so it should be running correctly.

Does anyone know what could cause this? Do I just need to replace the gauge or is it something more involved than that for this kind of fix?

 

[Highliner]

Pull the gauge and look at the back. There is often a little rotary switch that is used to select 4,6 or 8 cylinder application. When this switch gets dirty it can cause the issue you describe. Work the switch back a forth several times to clean up the contacts and see if that fixes your issue. A little contact cleaner would help as well.