Ignition Coil 584477 0584477

Function and Technical Context

The ignition coil is the component of the ignition system responsible for transforming the battery voltage into the high voltage necessary to generate the spark at the spark plugs, thereby initiating combustion in each cylinder. It operates within the ignition circuit of the outboard or inboard engine, synchronizing with the ignition module to fire at the exact moment of the engine cycle. A faulty coil causes intermittent or continuous ignition failures, difficult starting, notable loss of power, unstable idle and even sudden engine shutdown during navigation. This spare part with reference 0584477 is compatible with Johnson engines and with the ignition systems of Mercury, Mariner and MerCruiser that use references 802371 and 802371A1.

When to Replace This Part?

The most common symptoms of a faulty ignition coil are jerking or pulling during acceleration, failure of one or more cylinders (easily detected with a scanner or by disconnecting spark plugs), increased fuel consumption and difficulty starting in cold or hot conditions. It is recommended to inspect the coil at each seasonal service, especially if the engine exceeds 300 hours of use or has been in service for several years, as continuous heat and vibration progressively degrade internal insulation. Replacing the coil preventatively at the first signs of symptoms avoids being stranded and facing an emergency repair with much higher costs.

Equivalent Manufacturer References