Help tachometer not working

[yamaha_2000r6]

I have a 2003 monterey with a mercruiser 6.2mx with mpi injection. The problem is the tachometer does not function. It moves a little when you turn the key but doesn't go to 0 rpm's like its supposed to. When the boat is running it doesn't show anything. I've looked at the wires on the back of the tach and everything is connected. Does anyone know where to look on the ignition for the tach wire? Not sure what to check if someone has some ideas.