How to Troubleshoot Yamaha Outboard Gauges

A Yamaha outboard motor doesn't come with "all the bells and whistles." Rather, it comes with a tachometer and a set of warning horns. The horns are triggered by overheating, low oil pressure and other conditions that might cause the powerhead to rupture irreparably. This leaves the tachometer as the only gauge native to the Yamaha. Your troubleshooting will eliminate outside electrical problems, as well as mechanical problems within the tachometer.

Things You'll Need

  • Digital multimeter
  • Shop tachometer
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Instructions

  1. Wiring

    • 1

      Remove the tachometer's mounting screws. Lift the tachometer from the dash.

    • 2

      Locate the green wire on the back of the tachometer and ensure it is connected to the screw terminal marked with the letter "S." Locate the black ground wire that comes from the tachometer. Ensure that it's connected to the boat's common ground.

    • 3

      Turn a digital multimeter's selector dial to "Ohms" or "Continuity." Touch the red probe of a digital multimeter to the "S" terminal of the tachometer. Touch the black probe to the connection between the green wire from the back of the tachometer and the wire's connection to the ignition coil. There should be low or no resistance if the tachometer is electrically sound.

    Operation

    • 4

      Squeeze the clamp of an induction shop tachometer and hang the tachometer on the spark plug lead of the No. 1 spark plug.

    • 5

      Provide the engine with a water source. Start the engine. Allow the engine to warm up.

    • 6

      Note any difference between the reading on the shop tachometer and the engine's tachometer. If the shop tachometer varies from the engine tachometer by more than 200 rpm, replace the tachometer.