High-performance marine spark plugs designed for Mercury 3-cylinder and 4-cylinder 4-stroke SOHC engines. Precision-engineered with nickel-plated shells and corrosion-resistant electrodes for extended durability in saltwater environments. Features triple-gasket sealing to prevent combustion leaks and optimized heat range for consistent ignition under heavy loads. Ideal for fishing boats, pontoons, and recreational watercraft requiring reliable cold starts. Copper-core construction ensures rapid heat dissipation during prolonged high-RPM operation. Direct OEM replacement with exact thread pitch and reach specifications. Bulk packaged for commercial marine repair shops or fleet maintenance.