Mercury – Spark Plug Wires | V12 Verado & SeaPro Series | Marine-Grade | 8M0178258Mercury 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