NGK UR4 SPARK PLUG

Function and technical context

The NGK UR4 spark plug is part of the ignition system of the outboard engine, being responsible for generating the electric spark that ignites the air-fuel mixture in each combustion cycle. It works inside the combustion chamber subjected to extreme conditions of temperature and pressure, so its construction is designed to guarantee consistent ignition in marine application engines. A bad spark plug causes misfires, a noticeable loss of power, increased fuel consumption and, in serious cases, damage to the catalyst or the engine cylinders themselves. Its correct selection is especially relevant in high-end outboard engines such as the OMC Cobra, where ignition precision directly influences performance and reliability in navigation.

When to replace this part?

The most common symptoms of a worn or defective spark plug are: difficult or irregular starting, jerks and power losses at different speeds, increased fuel consumption and, sometimes, abnormal vibrations in the engine. In marine applications it is recommended that spark plugs be inspected and replaced every season or every 100 hours of sailing, whichever comes first, as humidity and saline conditions accelerate electrode and insulator deterioration. Changing the spark plugs preventively at each seasonal service is a simple and economical measure that prevents breakdowns at sea and ensures reliable starting at all times.

Compatibility with OMC Cobra engines

Equivalent manufacturer part numbers