RPM reading wrong

[Rico23]

I have noticed a number of times where the reading on the RPM guage changes rapidly with no change in the throttle. It will spike from 4000 to 6000 rpm's when crusing along at the same speed. What do I need to check/replace to ensure I am getting the correct reading?

 

[Oshkosh1]

Re: RPM reading wrong

If your getting a reading...it's more than likely the tach itself. There's a knob on the backside which designates the type of engine. Turn this back and forth a couple of times then ensure it returns and "locks" at the correct setting. If this doesn't help, clean your connections and ensure they're tight. After those...and if it's an older boat, it's probably the tach.