Thanks for any advise, this board rocks.<br />Here is my problem.. I installed a Airguide Model 1023 New old stock Tack on my boat and the needle goes to Max rpms when i turn the key on. The motor is a Mercury 1500 150 hp inline 6 serial # 70581225 (canada) makes it 1975 or 76, The Tach came with the tach harness with plug in the wires from the harness are green, black & white...the Tach has only two wires green and black. I feel the white wire is for an optional light for the tach and I need a kit for that so I just hooked up the two wires green and black and no luck with it working right so i unpluged it. The Airguide box says this with work with my motor (year & size) any sugestions on this subject is welcome thanks.