Tachometer and cable connection

I bought a used 1994 115Hp V4 and would need the forum´s help for Tacho connection.
I have the following connection pins on the Tach.
G (seems ground) 4 B 12. B and 12 is bridged, I already identified that the green cable comming from the Control must be the Signal for engine speed. I already connected black to G and green to B, but the Tacho is still not working.
Is the yellow cable (+12V) also needed somewhere on the Tach.?
Can anybody provide me a wiring diagram. Thank you very much for your help in advance. Erik

[boats.net]

I don't remember seeing any thing like that. The G may be for green wire, B for Black wire and 12 for 12volts which would be the yellow.