Mercury - Gear Case Drain Screw Seal (Pack of 2) Gearcase Hardware Rubber-Coated Stainless Steel 8M0058391. Overview. When you've spent enough time on the water, you start to appreciate the small parts that keep everything running smoothly. They're easy to overlook, but they're also the ones that protect your gear when you're miles from shore or backing away from the dock on a quiet morning. The Mercury Gear Case Drain Screw Seal is one of those little essentials that gives you real peace of min