Mercury - Spark Plug Wire Kit Ignition System Marine-Grade Construction 863656A1. Overview. Every boater knows the small things matter most when you are out on the water. A strong ignition system is not flashy, but when it is right, you feel it instantly-your engine fires with confidence, the idle smooths out, and everything just settles into that familiar rhythm you trust. That is the comfort this Mercury Marine spark plug wire kit brings back. Whether you are easing out of the marina at dawn o