How to Test a Coil Pack With a Multimeter

The best way to test your outboard's coil pack is with a digital multimeter. The basic idea is to first test the continuity of the circuit between the coil and the engine control module. Then you test the continuity between the primary side of the coil pack and the secondary side of the coil pack. Finally you test the continuity between the coil pack and each spark plug.

Things You'll Need

  • Multimeter
Show More

Instructions

    • 1

      Disconnect the primary wire that leads from the engine control module to the coil. Set the digital multimeter to the resistance scale and touch the black probe to the engine block to establish a ground.

    • 2

      Touch the multimeter's red probe to the coil's primary wire connector on the coil, to test the continuity between the ground and the primary side of the coil pack. The resistance should fall between 0.05 and 15 ohms.

    • 3

      Touch the multimeter's black probe to the coil's primary connector on the coil's primary tower, the side to which the wire from the ECM is connected. Touch the red probe to the coil's secondary tower connection, from which the spark plug wires go to the spark plugs, to test the continuity between the primary and secondary sides of the coil pack. The resistance should fall between 225 and 325 ohms for motors under 70 horsepower and 15,000 and 20,000 ohms for motors greater than 70 horsepower.

    • 4

      Grasp the spark plug wire at the plug. Simultaneously twist and pull on the spark plug wire's connector to remove the wire from the plug. Insert the red probe into the plug wire's connector. Resistance between the secondary side of the coil pack and the connector that fits onto the spark plug should lie between 2,100 and 4,100 ohms.