CHAMPION RC9YC4 SPARK PLUG

Function and technical context

The spark plug is the fundamental element of the ignition system in outboard engines, responsible for generating the electrical spark necessary to ignite the air-fuel mixture inside the cylinder. This component works under extreme pressure and temperature conditions in each combustion cycle, being subjected to intense mechanical and thermal stresses during engine operation. In ignition systems of Yamaha engines and similar medium to high displacement engines, the spark plug is critical to maintaining consistent ignition and efficient combustion. When a spark plug degrades, the spark weakens, causing incomplete and irregular combustion, which directly translates into loss of power, increased fuel consumption and difficulties in starting the engine.

When to replace this part?

The main symptoms of a worn spark plug include difficult or irregular starting, stuttering and loss of response at low rpm, misfiring under maximum load and appreciable increase in fuel consumption. It is recommended to check and inspect the spark plugs during each seasonal maintenance, and replace them preventively every 100 hours of operation or annually according to the general nautical maintenance standard. Changing spark plugs preventively is one of the most economical interventions in boat maintenance and avoids costly breakdowns at sea that can compromise navigation safety.

Equivalent manufacturer part numbers