Mercury - Spark Plug Wires V12 Verado & SeaPro Series Marine-Grade 8M0178258. Overview. When you run a big outboard - especially a V12 - you get used to relying on parts that just work. Spark plug wires might not be the first thing you think about when you push the throttles forward, but you definitely feel their influence every time the engine lights off clean, smooth, and strong. The Mercury 8M0178258 Spark Plug Wires are built with that exact kind of trust in mind. They give you the comfort o