Mercury – 815407T5 Ignition Rotor and Cap Kit | V6 GM MerCruiser Engines | Thunderbolt IV & V HEI Ignition | 815407T5Mercury 815407T5 Ignition Rotor and Cap Kit V6 GM MerCruiser Engines Thunderbolt IV & V HEI Ignition 815407T5 Overview When your engine lights up instantly and runs smooth from idle to plane, youre hearing the sound of a healthy ignition system. The Mercury 815407T5 Ignition Rotor and Cap Kit helps keep it that way. Built for marinized GM based V6 MerCruiser engines with Thunderbolt IV and V HEI ignition systems, this kit restores strong, consistent