What Do I Gap My Spark Plugs at for a 91 Johnson 115HP?

When you need to gap the spark plugs on a 1991 Johnson 115-horsepower outboard, the right distance between the electrodes is only part of the process. Even new plugs require an inspection before they are installed. Once you have completed the visual inspection, a quick check of the spark gap with a wire gauge will reveal whether minor adjustments to the plug are necessary.

Things You'll Need

  • 0.30 wire gauge
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Instructions

    • 1

      Inspect the plug visually for cracks in the ceramic insulator. Look at the end of the ground electrode that arcs over the center electrode. The end of the ground electrode and the flat tip of the center of the electrode must be parallel.

    • 2

      Grasp the plug by the insulator. With the other hand, try to pass a 0.030 wire gauge through the gap between the center electrode and the ground electrode. If the wire gauge passes through the gap with a slight drag, the plug is properly gapped.

    • 3

      Bend the ground electrode toward the center electrode, using the bending tool attached to the wire gapping gauge, if the gauge passes between the electrodes freely. If the gauge drags heavily or won’t pass between the electrodes at all, bend the grounding electrode away from the center electrode until the gauge passes with a slight drag.

    • 4

      Test the gap with the wire gauge. Rebend the ground electrode, if necessary, until the gap is correct.