1996 Speedster RPM gauge stopped working

[06330i]

So I was out on the boat today, pretty rough out there, and about half way through my trip, my starboard rpm gauge stopped working, the port side still works, where do I begin to check to fix this?? When you put the dess lanyard on both gauges still reset and drop down to 0 rpm's. thank you.

 

[06330i]

Figured it out, the wire that goes on that 4 wire harness into the motor was corroded off, had to hardwire it in and its fixed now.