Mercury - NGK LKAR7C-9 Spark Plug Ignition System Trivalent Metal Finish. Overview. There's a special kind of confidence that comes when your engine fires instantly-no stumble, no hesitation, just a clean, steady start that sets the tone for the day. The right spark plug is a big part of that feeling. This genuine Mercury Marine replacement plug is built to deliver consistent ignition in the marine environment, so whether you are launching at dawn or cruising back to the dock after a long run, y