CHAMPION RS9YC SPARK PLUG

Function and technical context

The Champion RS9YC spark plug is part of the engine's ignition system and its mission is to generate the electric spark that ignites the air-fuel mixture in each cylinder at the precise moment of the combustion cycle. On 5.8L OMC outboard engines equipped with electronic fuel injection (EFI and EFI-HO), timing and spark quality are especially critical, since the control unit manages the injection based on dynamic parameters that require perfectly consistent ignition. The electrode of this spark plug is calibrated to maintain the correct spark distance under the pressure variations that occur both at idle and at full acceleration, guaranteeing complete combustion that translates into energy efficiency, reduced emissions and sustained performance. When a spark plug deteriorates in a marine environment, continued exposure to humidity and saline environments accelerates the corrosion of the electrode and ceramic body, so its resistant construction is decisive for the reliability of the propulsion assembly.

When to replace this part?

The most common symptoms of a worn or bad spark plug are: difficulty starting when cold, jerks or misfires at different speeds, increased fuel consumption and perceptible loss of power, especially at high load. In engines with EFI systems, an ignition failure in one or more cylinders can also activate the engine warning light. As a guideline maintenance interval, marine engine spark plugs should be inspected at each seasonal inspection and replaced as a preventive measure approximately every 100 hours of use or following the guidelines indicated in the manufacturer's manual. Changing spark plugs preventively before they fail avoids compromised situations at sea and preserves the useful life of the ignition coil and injection system.

Equivalent manufacturer part numbers