Tach wiring help

"I have an old tach I want to

"I have an old tach I want to install on my 86 Glasstream I/O with a 120hp chev engine. The tach has 4 wires,1 red, 1 white, 1 black,and 1 green. Where do I connect these wires? Thanks, Jerry"

forget colors. who knows what

forget colors. who knows what somebody stuck on there. terminal I=ignition. 12v+(switched) G= ground. S= send. to coil neg. the fourth wire is for guage lighting.

"Jerry:

If you can find a n

"Jerry:

If you can find a name and model number or serial number on the tach., Google the tach. name and search their site for the tach. or its replacement. You may have to call them or send an email to get the wire connections.

If you can't find it do the following:

Black wire will be the ground wire.

The other colors are not listed in my manual.

In your dash there should be a gray wire from the coil negative terminal to connect to the tach. wire. Which one?

Simple procedure to ID wires; connect the black wire to the negative terminal of a 6 volt lantern battery. Take another wire and connect it to the positive terminal of the 6 volt batt. Use that wire to connect BRIEFLY to each of the other wires.

One wire will make the needle of the tach. move left or right. That is the tach. wire to connect to the gray dash wire.

One wire will turn on the light in the tach. That is the 12 volt power source for the tach. and gets connected to either a dark blue or purple wire that you will see in the dash jumping from gauge to gauge.

The last wire will either be a separate 12 volt source for the tach. or part of the lighting circuit. That one you'll need to figure out."