Lower Gearcase Seal & O-ring 18-0584 18-0586 18-0585 25-33145 For Mercury 6-15HP

Lower Gearcase Seal & O-ring for Mercury

This lower gearcase seal and O-ring kit is built to replace worn seals on Mercury 6-15HP outboards, citing OEM cross-reference numbers 18-0584, 18-0586, 18-0585, and 25-33145.

Overview

The lower gearcase seal and o-ring set is a direct replacement for Mercury outboards in the 6-15HP range. This lower gearcase seal and o-ring kit ensures a tight seal between the gearcase halves, keeping lubricant in and water out. It is an essential service part for maintaining the lower unit of your Mercury motor.

Built For Performance

• Precision-molded rubber compound for a snug fit
• Includes both seals and O-rings for complete coverage
• Corrosion-resistant material for marine environments
• Meets OEM specifications for reliable sealing
• Easy to install with basic hand tools

On-The-Job Use

• Replacing worn seals during lower unit service
• Preventing gearcase oil leaks that can lead to lower unit failure
• Maintaining watertight integrity when used on Mercury 6-15HP outboards
• Ideal for routine maintenance or rebuild projects

Specs At A Glance

Good To Know

Q: Will this seal kit fit my Mercury 9.9HP outboard? A: The kit is designed for Mercury 6-15HP outboards, but serial number differences can affect fitment, so always confirm compatibility before ordering.

Q: What is the difference between a seal and an O-ring? A: The seal prevents oil from leaking between the gearcase surfaces, while the O-ring provides a flexible seal around the shaft or cover. Both are included in this kit.

Slight variation in finish or dimensions may occur between production runs, and fit can depend on serial number, so confirm compatibility before ordering.