How do I add a tach to my 75 Johnny 135?

[Mikeyboy]

I have a 75 Johnson 135 horse motor with no tach. There was a tach in the boat when I bought it but it was not hooked up don't know if it ever was. The p/o had a bunch of gauges in it that they said were put in to look cool. I really want to put a tach in but have no idea how to hook one up. Can anyone help?

[AEROCOOK]

Not sure about that vintage but most OMC throttle control units that I've seen have a plug receptacle on them that the tach wires plug into.

[Mikeyboy]

I will check that out. Thanks for the tip.

[emdsapmgr]

Should not be too hard on your engine. The factory left a single grey wire loose inside the control box. This is the tach signal wire from the engine. You can pull that stub wire end out of a hole at the bottom of the control box. Each half of the box has half a hole-you will see the hole right along the split line between the two box halves. That wire can be extended to the S (signal) post on the tach. Now all you need is a pos and neg, from the dash and a wire for the light-if you want to run it at night. You will need a marine type tach, with the needle on the back set at "6".

[Mikeyboy]

Great thanks for the info. I really need to get a tach on it to help diagnose the problems I'm having.

[Steve079]

there is a product called "Tiny Tach" Wrap a wire around a spark plug, ground the other one, and voila, you have RPM"s and an hour meter. Less then 50 bucks.

here is the product website, hope its ok to post this
Tiny Tach

[Mikeyboy]

Thanks Steve I'll look into that.