Hooking up tach on 1975 johnson 50hp

[Tater72958]

Im about to purchase a tach for my 1975 johnson seahorse 50hp. It has a switch for 4, 6,10&12 pole on the back. Will this work on my 2 stroke 2 cylinder??
And where do i hook the signal wire to?

 

[F_R]

There should be a grey tach signal wire in the remote control. It comes from one side of the alternator rectifier on the motor.

Pretty sure the 50 is a 10 pole. Somebody will correct me if I'm wrong.

 

[Tater72958]

Ok so i got the tach hooked up and set to 10 pole. I think its off tho. At idle its seems ok but at WOT im turning around 6500rpm. I know my 16ft flat bottom is small but its also pretty heavy. Its 1/2 plywood decked from front to back.
Do i need a steaper pitch prop or should i try something else?