How to Test a Starter Solenoid for a Boat Engine

How to Test a Starter Solenoid for a Boat Engine

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You're looking forward to a day out on the lake in your boat. The weather is perfect with the sun reflecting off the gentle ripples on the azure water. What, you ask, could possibly spoil this pristine moment in paradise? You recover from your momentary reverie and turn the ignition key to start the engine...and nothing happens. You try again and hear -- nothing, except the pop of that imaginary bubble containing that perfect day out on the lake. Let's run a few tests to determine if you may have a faulty starter solenoid.

Items you will need

  • Multimeter

  • Small open end wrench (10mm - 12mm)

  • Wire brush

Check the battery voltage by first turning the battery switch to off and applying a small open end wrench to disconnect the positive and negative battery leads. Turn on your multimeter and twist the selector knob to the nearest voltage scale higher than 12 volts. Test across the battery posts, being careful to touch the black (-) probe to the negative terminal and the red (+) lead to the positive terminal. The reading should be at least 12 volts. 11.7 volts or less indicates a dead battery.

Inspect the battery cables for corrosion and loose connections. Seemingly good cables may have corroded underneath the protective insulation or broken under the battery post connectors, which will prevent the battery from delivering its full voltage to the starter solenoid. Clean the connections and posts with a wire brush. Reattach and secure the battery cables and with the transmission in neutral, rotate the battery selector switch to the "on" position.

Turn the ignition key to start. If you hear a clunking noise coming from the starter, it's the solenoid trying to do its job and there is probably nothing wrong with it. No sound indicates a possible solenoid problem that requires further testing. Make sure the multimeter is turned to the proper volts scale and the boat transmission is in neutral.

Disconnect the ignition lead at the solenoid. This wire is much thinner than the thick battery cable solenoid connections and will be attached to its own terminal on the solenoid casing. Attach the positive (red) probe of a multimeter to the end of that ignition wire and the negative (black) probe to any grounded metal such as the engine block or starter casing.

Ask a friend to crank the engine with you in the engine room observing the meter. If the multimeter reads 12 volts, that means your solenoid ignition terminal is receiving the proper voltage to activate the solenoid, signifying a defective unit.


  • For hands-off testing with a multimeter, attach two alligator connections to each end of a three foot long length of insulated double strand lamp wire. Then, separate the wires at each end, but leave them connected near the middle of the three foot length. Now, when you're testing, you can clip the alligator connectors to the meter probes and the other clips to the device being tested, leaving you hands-free.
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