Mercury Tach Module Wiring

[Jaynen]

Hello
Having trouble finding stuff on the net about this. I am trying to wire up the tach for my boat but not quite sure which wires to connect and where. In the following picture I got numbers for the wires if anyone can help me connect them. Also there is this tach module which I dunno if I need or not. Any help would be greatly appreciated.

 

[Barnacle_Bill]

Re: Mercury Tach Module Wiring

It would really help to know exactly what motor you are working on and what tach you are trying to hook up.

 

[Jaynen]

Re: Mercury Tach Module Wiring

The tach has no info on it anywhere, and I can't adjust the pulse on it. The motor is a 1974 merc 500 with thunderbolt ignition and mercontrol box. Just need to know how to wire what I got in the picture. I got the wiring diagrams for everything else.

 

[Jaynen]

Re: Mercury Tach Module Wiring

Anyone have any idea? I know its simple just wanna make sure I hook it up right the first time.

 

[chum1]

Re: Mercury Tach Module Wiring

you have a distributor style engine and need to verify that tach will work, i think you need a 12 pole tach, as far as the wiring goes good question.

 

[Jaynen]

Re: Mercury Tach Module Wiring

This is a picture of the tach module. Am I right to be thinking that the tach itself has no selection for how many poles and you just wire in this tach module along the send wire to give the tach a proper signal? So I am gonna wire 2 to 9 and then 8 to either 6 or 7. I am hoping 6 and 7 that one is just a light for a backlight on the gauge. Should my tach be reading zero when its unplugged or plugged in? Cuz it seems like its always at 1000rpm no matter what. Do I need to have this module?

 

[Jaynen]

Re: Mercury Tach Module Wiring

Bump

 

[Jaynen]

Re: Mercury Tach Module Wiring

So I have tried everything to test this tach and the tach is dead. So I am gonna buy a new tach. My motor has the lightning energizer ignition so can I buy a normal tach and put this tach module inline of the send wire for the new tach to protect it and have it work? Or do I have to run a new wire right from the back of the engine for a new tach?

 

[merc850]

Re: Mercury Tach Module Wiring

I think that your tach connects to the ignition and the module is for breaker points on the older models but I don't know the method, do you have a local Mercury dealer that would help you? I think that the 1965 to 1974 manual has the info you want.
If you buy a marine tach it will connect to one of the yellow wires on the alternator.

 

[Jaynen]

Re: Mercury Tach Module Wiring

I went ahead and tore apart the internal engine harness. Found some info on this site and got rid of the spliced tach and engine ground wires. Now I can hook up any tach I want and still got the factory tach plug at the control box. Great site, thanks for the reply.