Mercury - Quicksilver Outboard Switch Box Assembly Ignition System Component 3- & 6-Cylinder 2-Stroke Outboards 7778A12. Overview. If your ignition system starts misfiring or won't hold a steady spark, it might be time to replace the switch box. The Mercury Marine 7778A12 Quicksilver Outboard Switch Box Assembly restores smooth ignition timing and consistent spark performance for 3- and 6-cylinder Mercury and Mariner 2-stroke outboards with ADI (Alternator Driven Ignition) systems. Each unit is