The tachometer on my Yanmar
3GMF has started jumping around a lot. It will hold steady and give good readings through about 1100 RPMS. Then, as I accelerate, it will start jumping between 0 and 2000 and never give a reliable reading again until I drop back to under 1100 RPMS. I have cleaned and checked the wiring
and connections to no avail. I am now faced with replacing the sending unit ($100+) or the Tacometer ($200 +) or both.
Does anyone have any further troubleshoooting suggestions, to help me determine rather it is the sending unit or the tacometer or something else that needs replacing?