can anybody tell me how to start trouble shooting an erratic analog tachometer on a mako195 dc with a merc 150 efi. the gauge does respond a little bit but is doing this really weird bermuda triangle thing where it jumps all around.
I had a similar problem. I tried the expensive route (new VRR) first, but that didn't fix it. Next attempt I replaced the tach and all was well again. Mine would jump around for no reason sometimes, even when the engine speed didn't change. I could tap on the tach and it would sometimes work alright for a while. Then act up again. In the end...was a bad tach. Hope this helps.
If the tach has a pole or phase select switch, trying moving it to all the other positions, then back where it was. Sometimes the switch gets dirty.
If your battery is charging, and you have a dual regulator system, try moving the grey wire to the other regulator. One regulator (with the tach connected) could be bad. been there, done that.
I had a similar problem. I tried the expensive route (new VRR) first, but that didn't fix it. Next attempt I replaced the tach and all was well again. Mine would jump around for no reason sometimes, even when the engine speed didn't change. I could tap on the tach and it would sometimes work alright for a while. Then act up again. In the end...was a bad tach. Hope this helps.
My tack done the same as you said took to shop and they said it was the tack. I replaced the tack and now it does not work at all. I also replaced the (VRR) but it still don't work. Can you help me.
mercury 150 efi tachometer
Re: mercury 150 efi tachometer
Linear Mode
