Mercury - NGK IZFR5J Laser Iridium Spark Plug Ignition System Component 892567Q. Overview. Some parts work quietly in the background, but you feel their impact every time you throttle up. A spark plug seems simple, yet the right one brings your engine to life with clean, confident ignition. It smooths out the idle, sharpens throttle response, and keeps the entire power curve feeling steady. This Mercury Marine part delivers that familiar sense of dependability-the kind boaters notice the moment