View Full Version : new tach for my boat

09-29-2015, 10:17 PM
I bought a new tach for my boat I have a 1975 wellcraft V20 steplift with a 1975 115 Mercury 2 stroke O/B I'm not sure how the wires go. I have the harness from the old tach there are 3 wires bat, grnd and sender. I enclosed

a pic of the new tach . the dial on the old Tach was set to alt but the new Tach doesn't have alt what do I set it to

09-30-2015, 06:06 AM
Assuming you have the three wire harness from the control to tach,brown to signal,black to ground-,white to pos+ and set at 6P.

09-30-2015, 06:41 AM
PUSH in on that adjustment to turn it--don't just turn it. And wiggler it back and forth at '6P' to ensure a good contact.


09-30-2015, 03:33 PM
I just had a thought,is the brown wire at engine side on the rectifier?Reason for asking,some of the older Mercs have a brown post on the switchbox where the sig wire used to go.If,by any chance it is there,move it to either of the poles with the stator wires on the rectifier

10-01-2015, 06:05 AM
Usually the stator wires on Mercs are yellow. Pick one of them and, if the needle doesn't move, try the other one. Had to do that twice (for some reason).