I'm with Jeff (look in the installation manual first for a wiring detail) and then I'm with those that vote for finding a user variable set up in your engine monitor and hand held tach.
In my case I first found the set up in the EFIS and engine monitor and no problems. Then, some weeks later an issue with the "RPM" going over 9,000 got my attention. That's when an engineer at B&C read the manual correctly for me. After I installed the wires and a resistor correctly my problem went away and stayed away.
Good luck, let us know your final solution.