Connecting tachometer

[amware75]

Evening, I need some help connecting my old school tachometer. I recently purchased a 1971 Arrow Glass Cheetah. It has a 1998 Yamaha 115hp 2 stroke engine. All gauges work except the RPM gauge. How do I connect it? Thanks

 

[wrench 3]

There should be a green wire in a harness coming out of the control box. The harness will also contain a yellow, black, and a red. The green is the signal wire for the tachometer. Power and ground can come off of the other gauges.
I'm afraid I can't tell you what the gauge setting should be.