I have a 4 stroke, 90 H.P. Merc on a 19' Alumaweld Stryker and the only gauge I have on my dash is a fuel gauge. I would like to put on a Tach, Water Temp or Pressure and Volts. Mt delemma is that I have no clue on which wire to use on the harness to accomplish this, all I have are a bunch of...