Mercury - Quicksilver NGK IZFR6J Laser Iridium Spark Plug Marine Ignition Component Sold Individually 843220Q. Overview. The Quicksilver 843220Q NGK IZFR6J Laser Iridium Spark Plug is built to give your Mercury outboard dependable starts, smooth power, and long service life. It's the same high-quality plug trusted by Mercury Marine for factory performance, designed to handle the heat and vibration of real-world boating. Each plug comes pre-gapped and ready to install, so you can get back on the