Erratic Tac

[Fl_Richard]

1995 Johnson 150 twin's -- Dual batterys, battery switches, etc.-- essentially factory wiring. Dual tachs often register higher than actual RPMs. Tapping Tach'S will make needle jump then eventually read correct RPMs. This will happen to both tachs, sometimes at the same time, sometimes independantly. But on every outing. Is this a 10+ year old tach issue (x2) or an engine electrical problem?

Many thanks,

Rich

 

[Silvertip]

Re: Erratic Tac

Not likely that two engines develop the same problem at the same time. This sounds like an instrument problem since taps seem to make them behave differently. Ensure the wiring to each tach is tight and corrosion free. Next I'd rotate the calibration dial on the back of the tach through the various settings and then return each to the original setting. See if that helps.

 

[Fl_Richard]

Re: Erratic Tac

Excellent idea!!

Thank you, I'll try that and report my findings

 

[Fl_Richard]

Re: Erratic Tac

Well Cappy...

Spun the calibration dial a few clicks and after several hours of enjoyment they are both solid as a rock. They havent had an errant reading yet

Many thanks!!!!

 

[fla. water dog]

Re: Erratic Tac

please check the wiring (Grounds).. If you lived in florida, it would have happened years ago....