Connect tachometer

[Ricky_rich]

Just to make sure, how would I connect the cables on my tachometer?
Mercury 1150 1970
Three cables from the controll box
White for light
Brown cable to red connector?
Black (ground) to one of the other?

 

[Bigreddon]

The three wires from you controller are 1) 12v
2) negative
3) tach signal

Use a 12v test light. The negative of your test light (clamp) goes to ground. The probe of your test lamp will then go into each connection of your controller connector. One will light up. That's the 12v.
Once you've found the 12v, leave your test light probe there. Remove the test light cllp from your ground, and put a paper clip in your test light clamp. Now, move the paperclip to one of the two other connectors. Once your light turns on, you have located the negative.
The remaining connector is your tach signal.
You may have to have your key/ignition "on" to do this test.
Should take all of 1 minute to do.

 

[Ricky_rich]

Ok so now I know that I have the following from the controll box.
White +12v (to instrument light)
Black is ground
Brown is signal

This is what my tachometer look like on the back.
So where do I connect the black and brown cables?

 

[Chris1956]

That might be one of the real old Merc Tachs. You might google the number and see what you find. Those oldies hooked up the switchbox instead of the stator, like the modern ones.

 

[Ricky_rich]

Can not find anything useful about ths tach on the net. Barely anything...
I'm afraid that I will destroy the tach if I don't connect things right?
My idea for a connection is following. Could this be a safe way to go?

Black (ground) to instrument housing
Brown (signal) to black connector on instrument
External +12v supply to red connector on instrument
White goes directly to lamp holder so that one is given.

 

[Chris1956]

What is the brown signal wire connected to on your motor? I think it should be the switchbox. I would PM one of the real experts on this forum, as I cannot offer any enlightened opinion. These Tachs come up from time to time, and someone should know the answer. You do not want to destroy your switchbox.

 

[Ricky_rich]

Yes the brown signal cable connects to the switchbox.
Any idea who to contact?