Mercury - Quicksilver 816575A3 Gear Case Seal Kit MerCruiser Alpha One Gen II Sterndrives 816575A3. Overview. Leaks and water intrusion can do real damage to your drive, but the Quicksilver 816575A3 Gear Case Seal Kit helps keep that from happening. Designed for MerCruiser Alpha One Gen II sterndrives, this OEM kit includes every seal, O-ring, and gasket needed to restore a watertight fit and protect your gears from contamination.. Each piece is built to Mercury's tight tolerances using marine-g