View Full Version : off the wall ?? mercury tach
marcdups
09-30-2004, 11:05 PM
where does a mercury 250 hp efi 1999 model get it's tach signal from, is it the alternator or the ecu??or the flywheel sensor?? I cannot think about outboards as we are installing twin Cummins in a dive boat right now and after having John Deers in it modifications are quite intensive and he has two charters Saturday, :shocking: :shocking: :party: :outtahere
Fish boy
09-30-2004, 11:17 PM
DO you have a smartcraft gauge or are you using a standard gauge?
marcdups
09-30-2004, 11:21 PM
standard Fish, therefore I thought it would be the alt, as I could not find an external regulator/ rectifier, but voltage output is okay at all rpm's, just tack jumping all over the place, so ???
This may work try rotating the switch back and forth in the back for cylinder changes, sometime that helps by cleaning its contacts. I have resurrected a few condemned tachs doing that. Also check grounds.
marcdups
09-30-2004, 11:32 PM
MOP tried new tach with same results ??
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