Mercury - QL78V Spark Plug (4-Pack) Ignition Component Copper Core & Ceramic Part Number 896329838. Overview. There's something incredibly reassuring about an engine that fires to life without hesitation especially when you've got a long day on the water ahead of you. The Quicksilver QL78V Spark Plug brings that confidence back to your Mercury Marine engine. It's one of those small parts that quietly influences every moment on the water: the smooth rumble as you pull away from the dock, the cris