Saltwater series II need help with tach wiring

Hello -
I just bought a used Yamaha 250 Saltwater Series II engine. It come w/ the starting panel, tachometer and wiring. I am able to get the engine running, but I can't get the tachometer to work. It doesn't display anything. I don't know if I wire it correctly or not. I am not sure about some of the wires coming out of the tachometer. I attached two pictures can you take a look and tell me what are those wires are for?
This is the first time I own an outboard motor so any help is much appreciated.

Thank you very much.

[jb123]

looks like you need the fusable harness from keyswitch to those 4 wires.

looks like you need the fusable harness from keyswitch to those 4 wires.

Thanks for the quick review and response.
Do you mean one or some of those wires provide 12v power to the tach? If so, which wire or wires get the 12v power? Can you tell where each one of those wires go?

[jb123]

the blu n blk are for back light, the blk grnd ,yel 12v and grn tack signal

the blu n blk are for back light, the blk grnd ,yel 12v and grn tack signal

thanks again. I still not sure where to connect the "grn tack signal" to. Is that the "tach signal" coming from the motor or does it goes to an external display?


Do you know anything about the extra blue wire that does not connect to anything inside the engine cover?

[boats.net]

The harness that JB123 is talking is part number 6Y5-83553-N0-00 thats connects to key switch and provides tach signal, key on power and ground. The blue wire under engine cowling has nothing to do with gauges, it's a choke wire for models with electric choke.