omc tach wiring question.

[misery]

So i know the tach thing has been beat to death on this site but i'm gonna ask this question anyway.
I finally have my 90hp ruddy working like a trooper, but my tach isn't hooked up. Its an omc tach with four wires. the light works and the needle will flinch when I feed it power so i think the unit is good. My problem is the plug in on my control box. i have the amphenol plug in but at some point in time the wires were cut off flush at its base. the male side of the plug in has the letters abc on the back. Which wires go where? I know that the grey wire is the Tach signal and the others are pretty easy. But in what order from left to right should i run this plug in. the female side of the plug in is built in to the control box and from the looks of the screws it won't be coming apart anytime soon so i can't see the wires inside the box.
Also I've read alot about the settings on the back of the tach, but mine has no such dial on the back of it. it has a rubber plug covering a small circular piece of metal with numbers around its circumference,but it is fixed and is not adjustable. does this mean that the tach is mated to this motor and needs no setting changes? I can't say for certain that this is the original motor to this boat or that the tach is the tach for this motor.

 

[Sixmark]

Re: omc tach wiring question.

I would suggest taking your control box apart anyhow, dont worry about the screws as you can replace them, you have no way of knowing if anything is hooked to the plug inside the box, and being that somebody hacked the wires off the exterior plug I wouldn't be very trusting of the internals.

Grey is the tach signal wire, purple is the 12v accessory, black is ground, you will have to check your tach and see if the 4th wire is for the light or not, if it is, then it's your choice to wire it to the ignition or to an instrument light switch on the dash panel.

The little piece on the back of the tach with the numbers around it would normally be the adjustment, but you said it is fixed, if that is the case, you can try hooking it up and see if it works, or you can get a new tach.

It would also be helpful to have a model number for the motor so we know what year and type we are working with.

 

[emdsapmgr]

Re: omc tach wiring question.

You'll need a marine tach for that engine. A car tach won't work. The marine tachs have an adjustment screw on the back which can be set for the type of engine, including stern drives as well as outboards. Your tach should be set on 6 in order to read correctly.

 

[misery]

Re: omc tach wiring question.

Thanks for the input guys. the motor is a 1986 evinrude 90 hp vro. I assume that the tach is a marine tach as it is made by omc or at least it has omc stamped on the face. i'll see if i can get a pic of it if i can figure out how to put them up on the message board.