Problems installing my tach

[itsmeagain5789]

I purchased a 40hp 2000 Yamaha 2 stroke and I am having trouble wiring the multifunction tach that came with it. The guy said it was working fine on his boat, but I can't get it to work at all on mine. I did do some engine rewiring with the harness(organization purposes only). Engine starts and runs great. It is working as it should be, but whenever I hook up the tach to it, even when the engine is off and ignition is switched to on, I get a constant reading of 4000rpm and the temperature light is flashing. Nothing changes when I turn on the motor. As soon as I disconnect it from the engine, nothing shows up except for the big zero in the center. Could this be a wiring issue on my part or is the tach likely bad? I couldnt find a model number of the tach or harness, so here are pics. thanks
Edward

[itsmeagain5789]

so I was trying to troubleshoot, and I realized that I am missing an entire harness. The one that goes from the control box to the gauge. I decided to see if I could bypass the harness just to test the rpm's by connecting the two greens together, I still got nothing. I am thinking that the tach is more than likely broken, so I will probably be going analog. Can I just run a wire from the green to an analog tach and get my rpm's like that?
thanks

[boats.net]

6Y5-83553-N0-00 is the harness that connects to yellow, green, black and red wires at control box and the gauges connect to harness matching color wires, you will have to connect all the wires on tach to 6Y5-83553-N0 harness to make tach work.

[itsmeagain5789]

Well the only problem I see with that tachometer wiring is that it only has one black wire coming out of it. That harness looks like it is supposed to connect to two different black wires. Do you have any idea what I would do with the other, or if it would even work? thanks
Ed