Troubleshooting an Outboard Ignition System

If your outboard has a spark but won’t start, there are several troubleshooting tests you can run to find the answer to the starting problems happening with your motor. 

From simple stuff to more advanced diagnostic testing, here are some ways to troubleshoot the ignition system of your outboard. 

Check the Fuse

Many outboards are equipped with a main fuse that runs to the ignition system. 

Look for a bulb on the lead wire running to the ignition to find the main fuse. Open it up and check the filament. If it’s burnt out, you need to replace the fuse.

Test the Tilt Kill Switch

Your outboard may or may not have a tilt kill switch, but if it has one and it’s raised up too high, it’ll kill the motor. Look on the tilt trim assembly or the mounting bracket to find the tilt kill switch. 

Next, get a multimeter and set it to the low ohm test, then connect the two wires coming from the switch. Hold the switch horizontally like it would be in the motor if it were trimmed down. You shouldn’t see any current running through the switch. Next, hold it at an angle like the switch would be if it were tilted up, and you should see current flowing through the switch. If you see it open or closed when it shouldn't be, the switch needs to be replaced.

Some units have a kill switch, others have just a trim limit or trim sensor switch. The outboard pictured above has a sensor switch, but a kill switch would be in the same general location. 

Hook up the leads to the multimeter to the switch and see if it goes through a significant variance, such as going from 4 ohms to around 230, which is an indication that the sensor is working. 

Smaller outboards have a switch on the tiller handle with a wire running to the CDI, which is basically a ground for the test. Set the multimeter to ohms, then touch the negative side to a ground and the positive to the wire coming to the CDI. If you see continuity, the switch has failed and needs to be replaced. Double-check it by activating the switch or removing the lanyard to see if you get a low reading and if you don't, you need to replace it.

Test the Plug Wires 

If you already checked the spark plugs on your outboard, test the plug wires to make sure they’re also working properly. 

Connect a multimeter to each end of the plug wire, then set it to ohms and hold the wire taut and straight. The meter should read 0 ohms or close to it. Next, bend the wires and see if the reading changes. If it does, the wires inside might be failing and you should replace it. 

Test the Ignition Coils

Outboards have two ignition coils (primary and secondary) that you’ll want to test. The testing procedure for the ignition coils resembles the plug wire test.

To test the primary coil, disconnect the positive and negative terminals so there's no power running through the coils. Set the multimeter to ohms and connect the positive and negative terminals. Check the service manual for the resistance you need to see on this test, and if you're not getting that reading, the coil should be replaced. 

Test the secondary coil by connecting one end of the multimeter to the negative terminal, and the other side to the spark plug that comes in. Check the reading to see if it matches the manufacturer’s specs and replace it if it doesn’t.

Test the Stator

Find out from the service manual what the resistance range is for your particular stator. Next, set the multimeter for that resistance range to see if you get a pass.

A low reading probably means there’s a short in the windings, and if the reading is infinite, there’s a break somewhere in there. You need to replace the stator either way. 

Test the Regulator Rectifier 

The regulator-rectifier only allows current to pass in one direction when it’s working properly. Two wires go in, the positive and the ground. Disconnect those wires, as well as the three wires going to the stator (if it’s a three-phase setup).

Set the multimeter to the diode test, then connect the positive side of the multimeter to the negative terminal on the regulator-rectifier. Next, connect the negative side of the multimeter to each of the three connections coming out of the regulator rectifier to the stator. A positive forward reading in volts around 0.5 tells you the current is passing through the diodes as it should. 

If any of these tests fail, replace the unit, then test it in the opposite direction to make sure current isn’t flowing backward. Connect the positive probe of the multimeter to the positive terminal of the regulator rectifier, and the negative on the multimeter to each of the three conductors coming from the stator. An open loop tells you there’s no current traveling backward. However, if you get a reading that a current is going through, you'll need to replace the regulator-rectifier. 

Test the Turnkey Switch 

To test the turnkey switch on a larger unit, you may need to remove it first. 

Set the multimeter to ohms, then connect the positive side of the multimeter to the shut-off terminal wire, and the negative to a ground source and turn the switch on.  If you get an open circuit with the switch in the on position, the switch has gone bad and needs to be replaced.