RPM guage not working

[duanebarker]

"I recently purchased a Regal

"I recently purchased a Regal boat with an AD31B diesel engine. The RPM guage is not working. It reads very erratic. Sometimes pegged out, sometimes just alot more than is should under idle conditions. It is not a wiring connection issue to the RPM guage. Before I replaced the RPM guage, is there anyway to test with a meter to make sure it is the guage and not a wiring problem or alternator?"

 

[sirlespat]

I don't know the specifics

I don't know the specifics of your engine but many RPM guages use the ripple voltage on the alternator to determine speed. If your guage constantly reads over there may be a switch or a second connection to select a different divide ratio. Measure the input of the guage with a voltmeter (what have you got to lose)