No Power to the Starter Solenoid

One of the articles of faith you must accept in boating is that when you have a problem with your outboard, it’s often sudden and never convenient. This is the case when you have no power to the solenoid – the relay that acts as the interface between the battery and the starter. The first indication that something is amiss is that nothing -– not even clicking -– happens when you turn the key.

  1. The Electric-Start System

    • The wiring for your outboard’s solenoid is straightforward. Your boat’s starting battery is connected to the key switch. The wire from the starter lug on the key switch is connected directly to the solenoid. The solenoid has a single connection to the starter motor. In some outboards, the starter has a ground wire connected to the outboard’s chassis; in other models, the solenoid is grounded to the outboard’s powerhead through the starter and then through an internal ground in the solenoid.

    Process of Elimination

    • Not all starting failures result from a lack of power to the solenoid, but if you turn the key and the starter doesn’t turn over, the solenoid isn’t getting power. Finding out why it isn’t getting power is a process of elimination –- eliminating every potential problem leading to the solenoid,before deciding to replace the solenoid itself.

    Visual Inspection

    • Look at the connections. Ensure the battery cable is firmly connected to the battery and to the “B” lug on the back of the ignition key switch. Look at the cable; a frayed cable is losing power at best and shorted at worst. Pull on the red wire that’s soldered to the “S” key switch. Follow the wire, checking condition and connections, to the solenoid. Tug on the wire between the solenoid and the starter. Pull on the ground wire from the solenoid to the outboard’s chassis if one is present. Finally, return to the battery and tug on the negative wire, both at the battery and at its connection to the common ground. Replace the wires if they’re frayed and reconnect them if the connections are poor.

    Starting Battery Condition

    • You can ascertain the starting battery’s condition with a simple digital multimeter. Turn the dial on the multimeter to the “less than 20VDC” setting and place the red probe on the battery’s positive terminal and the black probe on its negative terminal. The multimeter should register between 12 and 14.8 volts of direct current.

    Solenoid or Starter?

    • A differential diagnosis between the starter and the solenoid begins with you removing the negative cable from the battery, just as a matter of safety. Disconnect the red wire that leads from the key switch to the solenoid. Turn the multimeter to the resistance scale – marked by the Greek letter “omega” – and touch the red probe to the red wire and the black probe to the starter. There should be less than 500 ohms of resistance. Set the multimeter aside and disconnect the lead from the solenoid to the starter. Plug the wire from the key switch into a new solenoid and attach the solenoid’s red lead to the starter. Install the two bolts that hold the solenoid in place, reconnect the battery and try to crank the engine. If you get no result, the problem lies with the starter. If it cranks, the problem is that the solenoid is bad.