I am trying to install a tach on my 1999 90 Merc ELPO (3 cylinder 2 stroke). boat is a 17' Trophy w/ Quicksilver top mount controls. I do not see any secondary harness for the tach wiring harness. I bought the boat used and the wiring is not the cleanest, fair amount of butt connectors and the like. Anyhow, I found a gray wire in a group of three unused wires but not sure if it the sensor feed. Is there a way to test it? I am scared to harm rectifier. Can I just hook it up to tach and worst case is tach does not work? Also I cannot find a terminal block on the motor joining the two yellow wires to a gray output, is that used on all merc outboards?
