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In an outboard engine's ignition system, the flywheel and the trigger coils work together to generate the necessary timing signals for the ignition system.


Here's a detailed explanation of the process:


  • Flywheel Center Hub Magnet: The flywheel is attached to the crankshaft of the engine. Embedded within or attached to the flywheel are the magnets. As the engine runs, the crankshaft spins the flywheel, causing the magnets to rotate around the engine.

  • Trigger (Coils): Positioned around the flywheel center hub are the trigger coils or a stator assembly. These coils are stationary and contain windings of wire. The trigger coils are designed to detect the magnetic field generated by the magnets on the flywheel.

  • Magnetic Induction: As the flywheel spins, the magnets pass by the trigger coils. According to Faraday's Law of Electromagnetic Induction, a changing magnetic field induces an electric current in a conductor. So, when the magnets on the flywheel pass close to the trigger coils, they induce a voltage in the coil windings.

  • Signal Generation: The induced voltage in the trigger coils is a pulsed signal that corresponds to the position of the flywheel (and thus the crankshaft and pistons) as it rotates. Each pulse represents a specific position in the engine's cycle.

  • Ignition Timing: The pulses generated by the trigger coils are sent to the Switchboxes. The Switchboxes and ECU use these signals to determine the precise timing for firing the spark plugs. By knowing the position of the flywheel (and the engine's pistons), the Switchboxes can accurately time the spark to ignite the fuel-air mixture in the cylinders.

  • Spark Plug Firing: The Switchboxes then send a signal to the ignition coils, which step up the voltage and send a high-voltage current to the spark plugs. This creates a spark at the precise moment needed to ignite the fuel-air mixture, ensuring efficient combustion and engine operation.


What happens if you have an issue with the center hub?

If the center hub magnets are 1) assembled incorrectly, 2) you have the wrong center hub, one from another motor, 3) have a cracked magnet(s), or 4) have spun the magnet; the improper position of the north and south poles would cause mis or double fires.


The Buckshot Racing #77 X-Ray Film Paper allows you to check the prop position of the poles.


On the Mercury V6 2.0, 2.4, and 2.5 Liter, the poles should be positioned:


1) on the leading edge of the second bolt clockwise from the keyway, and 2) on the trailer edge of the second bolt counterclockwise from the keyway.


Includes two (2) strips of reusable Buckshot Racing #77 X-Ray Paper.

2 Center Hub X-Ray Film Paper

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