Mercury - NGK IZFR5G Laser Iridium Spark Plug Ignition Component Steel & Ceramic 889597Q. Overview. There's a kind of quiet trust that builds between you and your engine once you've found a spark plug that never hesitates. The NGK IZFR5G Laser Iridium plug feels like one of those dependable little parts you install and forget - because it just works. You turn the key, the motor fires, and the day gets going without a second thought. Whether you're easing out of a no-wake zone or pushing toward o