2000 Yamaha F100 Tachometer not working correctly

[thebubba]

Thank you for any help you provide in advance. I just bought a 2000 Yamaha F100 outboard motor for my 17' Lund boat. I had a 1994 Mercury 115 HP on it and replaced it with this motor. I purchased a used set of 703 controls and hooked it all up according to the manual. I set my tachometer to 12 pole setting, which was the same as the Mercury. The engine runs perfectly, it charges the battery when running like it should with around 13 volts when I throttle up a little. The tachometer reads about 200 RPM's when idling and 1000 when I have the throttle full. Obviously this is not accurate. I then bought a brand new Yamaha tachometer thinking my old one was bad even though it worked fine with the Mercury. The new Yamaha tachometer doesn't work at all. I am completely stumped at this point. I really need a tachometer so I can make sure I am running the motor correctly and so I can prop it correctly as well. Where should I begin to look for the problem. I believe my tachometers are both good and I am confident I used the correct wires coming from the 703 controls. I don't know if I have a bad wiring harness coming out of the controls to the engine or something wrong on the engine itself. The yamaha manual is pretty much garbage on being helpful about something like this. Please help!