Wiring Harness

[mulliganmagic]

I have a simple question about tach wiring. I bought a wiring harness that matches my control box and tach. It has three wires white, black, and brown. Could anyone tell me which wires go where. I think that Black is ground but I'm not sure how to tell the difference between white and brown and sender and 12+ volts. Hopefully someone can help, thanks.

 

[Dunaruna]

Re: Wiring Harness

You list two different mercs in your sig, which one are we talking about?<br /><br />The reason I ask is that merc changed their color code somewhere in the 70s'.

 

[mulliganmagic]

Re: Wiring Harness

We're talking about the 1977 Merc 700.

 

[Dunaruna]

Re: Wiring Harness

Black - ground. Black should always be ground.<br /><br />White - Ignition '+'.<br /><br />Brown - Rectifer signal (tach signal or sender).<br /><br />Mercury used their own wire color code and it can get confusing. Also, previous owners may have replaced wires with different colors. The safest way to proceed is to check before you connect - turn the ignition on (engine off) and test the white for battery voltage. Use the black wire for a ground. If this test is O/K, the sender wire must be brown. Make sense? You can also trace the white wire back to the 'I' terminal on the ignition switch.<br /><br />Aldo