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?
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".