Rotor Thunderbolt V6 -Trigger Wheel | Sierra 18-5432 V6 Thunderbolt Rotor -Trigger Wheel | Sierra 18-5432 Rotor fits Mercruiser V6 marine engines with Thunderbolt ignition systems. Rotor and trigger wheel for V6 Mercruiser Thunderbolt marine distributors Replaces Mercury 13524A6, 13524Q06, 13524A4, 19405A4, and 90576A4