Tach help Please

[jarheadtex]

I want to install a second tach to ensure my rmp are correct. I have a mercruiser 3.0xl. Which wire on the coil do i use. Which wire on the coil do i use. There are 2 plugs, one coming from the distributor with a red and black wire and the top plug has a purple and gray wire which appear to be the wires that go to the current tach. Thanks for any help.

 

[solar7647]

Re: Tach help Please

I BELIEVE IT THE GRAY THAT GOES TO THE NEG (-) SIDE OF THE COIL.

Ooops hit cap lock.

 

[Lyle29464]

Re: Tach help Please

some one will correct me if I am wrong. But I think you can just do it all under the dash. just hook second tack to first one. wire for wire.