tachometer problem

[Katphyshe]

Help,
I have a Johnson 225,1990 model. The tach never worked perfectly since I got it but good enough that I didn't worry. It quit working about a month ago, so I took one that works out of my other boat and hooked it up....it doesn't work either. Where should I start looking for the problem, as I have no idea where the signal originates or how the tach works. Any help would be greatly appreciated.

[OhBoy]

I believe The "signal" originates from the Negative side of the coil.
You also need a Battery/Ignition hot and a ground.
Hope that helps.......

[Wgoodrich]

You should have a hot and ground then a signal wire that connects to the impulse wire of your coil that serves your number one cylinder.

Good Luck

Wg