CHAMPION RN5C SPARK PLUG

Function and technical context

Spark plugs are the final component of the ignition system in marine petrol engines: their mission is to generate the electrical spark that ignites the air-fuel mixture in each cylinder at the precise moment of the cycle. The Champion RN5C spark plug works within the engine's ignition system, acting as an interface between the high voltage generated by the ignition coil or module and the combustion chamber. In the marine environment, spark plugs are subjected to particularly aggressive conditions: extreme thermal cycles, constant vibration, saline atmosphere and high humidity levels that accelerate the deterioration of the electrode and the ceramic insulator. Poor ignition due to bad spark plugs directly translates into loss of power, increased fuel consumption, unstable idle and, in severe cases, impossible starting far from port, compromising the safety of the vessel.

When to replace this part?

The most common symptoms of a worn marine spark plug include difficulty starting the engine when cold, jerking or misfiring under load (misfire), abnormal vibrations at idle and high fuel consumption without apparent cause in the supply circuit. For marine petrol engines, it is recommended to inspect the spark plugs during each seasonal maintenance and replace them preventively every 100 hours of operation or once a year, whichever comes first, given that the saline environment accelerates corrosion of the central electrode and the ground. Changing spark plugs preventively before each nautical season is the most economical measure to ensure reliable ignition and avoid propulsion failure in open water.

Equivalent manufacturer part numbers