Mercury - Quicksilver Shift Cable Bellows Driveline Seal Ribbed Composite 74639A2. Overview. A watertight seal around your shift cable is vital for protecting your sterndrive from corrosion and internal damage. The Mercury Marine 74639A2 Quicksilver Shift Cable Bellows keeps water out of the shift cable opening, sealing the connection between your drive and transom assembly. Made from tough, flexible composite material, it bends with the drive's movement without cracking or tearing. Designed for