Thunderbolt Tach hookup

[roger3645]

I have a 1975 850 mercury and have just picked up a vintage thunderbolt tachometer made in the same year as the motor. The control box has the tach plug with the brown black and white wire. I don't have the wire harness to just plug in the tach. I want to hard wire to the wires in the control box. The tach itself has 4 post on the back 2 for mounting the tach and two others. One marked (+) and the other (-). I believe blk goes to neg and white to the pos post. Where does the brown wire go on the back of the tach. From the control box, the brown wire goes to the power pack. Thanks for any help! Roger

 

[Laddies]

Re: Thunderbolt Tach hookup

I don't know the part no. of your tach, but to hook up # 91-45294A3 the white is for the light only, looking at the back of the tach the blk goes to the lower right or in some cases to a termanal in the center the mount bracket is cut out on those and the brn goes to the lower left termanal marked - if the tach reads backwards reverse the blk and brn

 

[roger3645]

Re: Thunderbolt Tach hookup

Thanks Laddies I give that a try.