Yamaha 70HP 1983 Tacho problem

Hello,

I have a 1983 70HP Yamaha outboard and the the tacho fitted to my boat is for a much newer engine and wont work. I have purchased an aftermarket tacho (teleflex). There are various coulred wires coming out of the control box, does anyone know which wire is the one to attach to the tacho? Thanks in advance.

[boats.net]

Green wire is tach signal
Yellow wire is key on power
Black wire is ground
Set tach for 6 pole alternator for 70 hp engine.

Th*nks very much, I w**l try it the weekend.