Tach wiring harness, can I make my own?

[rsp95]

I have a 1974 Merc 50hp electric start and I want to install a tach. Do I need to purchase a wiring harness or could I make my own? Any help would be appreciated. Thanks in advance.

 

[Dunaruna]

Re: Tach wiring harness, can I make my own?

You can make your own. There should be a 3 pin plug at the end of the control box, that is the tach connection.

Brown - Tach signal.
Black - Ground.
White - Ignition hot (12v)

These are old color codes and do not apply to modern mercs.

 

[rsp95]

Re: Tach wiring harness, can I make my own?

Thank you Dunaruna. Last question is wire gauge. Is there a specific size I should use?

 

[Moody Blue]

Re: Tach wiring harness, can I make my own?

You can get the tach harness off ebay for next to nothing. I bought one a couple months ago for $9. See them all the time.

If you build your own, use 16ga wire. I think those 1/4" male spade terminals will plug in individually to the sockets on the front of the control box. Be sure to shrink wrap each wire and terminal then tie-wrap the three wires together to form a bundle. Less likely the individual wires will come unplugged that way.