Mercury – Fill & Drain Screw Kit | Gearcase Service Hardware | 22-8M0083059

Overview

This fill and drain screw kit replaces the hardware used to open and close the lower-unit gear-lube ports on many Mercury and MerCruiser gearcases. These small screws deal with repeated removal, exposure to heat, saltwater, and vibration, so over time they can round off, lose their sealing ability, or develop corrosion that affects how the gearcase holds pressure. Replacing them as a set keeps the drains sealing properly and prevents slow leaks that can lead to water intrusion—a major cause of gear-lube breakdown. It’s a simple kit, but it plays an important part in keeping the gearcase healthy.

Key Features

• OEM Mercury Hardware – Correct thread fit for Mercury gearcase ports.
• Includes Sealing Washers – Ensures clean, reliable sealing after each oil change.
• Corrosion-Resistant Finish – Built for long-term saltwater and freshwater use.
• Direct Replacement Kit – Straight swap for worn or damaged fill/drain screws.

Engine & Boat Compatibility

• Mercury outboard gearcases
• MerCruiser sterndrives
• Standard drain and fill ports
• Mercury gearcase service group

Performance & Practical Benefits

Fresh screws and sealing washers help the gearcase maintain proper pressure and keep water out—a critical part of protecting the gears and bearings. When screws get worn, they often leak just enough to allow moisture to mix with the oil. That leads to milky gear lube and heavier wear throughout the gearset. Installing new hardware ensures the ports seal cleanly after each service and reduces the chance of rounding out the screw head during removal.

Why Buy OEM

These screws match Mercury’s thread cut and sealing depth exactly. Universal replacements often fit loosely or don’t line up with the sealing surface correctly, which can lead to slow seepage. OEM screws also use corrosion-resistant material that stands up to repeated gear-lube changes without degrading.

FAQ

1. What are common signs these screws need replacing?
Rounded heads, rust, or leaks around the washers after a gear-lube change.

2. Should I replace both screws together?
Yes. Both are exposed to the same conditions and tend to wear at similar rates.

3. Are new washers required every time?
It’s strongly recommended; washers compress and lose sealing ability.

4. Can I install them with basic tools?
Yes—standard screwdrivers or hex drivers depending on the model.

5. Will this improve gearcase reliability?
Yes, by helping prevent water intrusion and maintaining proper sealing.