Without a strong, well-timed spark an engine won't start and run. This section covers how to test for spark and the main reasons why you may not be getting a good spark. The video below talks about testing CDI ignition systems while the topics to the right cover specific problems you may have with your outboard's ignition system.
The spark plugs are responsible for creating the electrical spark in the cylinder to ignite the fuel. Spark plugs are the only part of the system that requires periodic replacement.
The ignition coils on outboards are relatively simple, robust devices but they do sometimes fail. Internally they are windings of wire that can burn out and need replacing.
The exciter coil sits under the flywheel, where a magnet on the flywheel induces a small current in it. That current charges the capacitor in the CDI unit, so a faulty coil leaves it uncharged.
The trigger coil that instructs the ignition to fire is faulty
The CDI unit (Capacitor Discharge Ignition) is a sealed unit that fires each of the ignition coils coming from it at the precise moment required for optimal combustion.
The kill switch, or man-overboard lanyard, is used to stop the spark plugs from firing. This lanyard being unplugged is the most common reason for an outboard motor to not have spark.
Ignition timing that's badly out, such as from a sheared flywheel woodruff key, can stop an outboard starting. I explain why timing advances with RPM, then set the idle and full-advance timing stops.
Making a direct voltage adapter (DVA) to test CDI ignition
A peak voltage adapter lets a multimeter read the peak voltage from ignition coils and the CDI unit. I build a cheap one, check it on a power point, then modify it for testing CDI output.
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