Lower Unit Seal Kit for Johnson/Evinrude 85, 100 & 125 HP 2-Stroke Outboards — Large Prop Shaft — Replaces Sierra 18-2691 and GLM 87611

Product Details

This aftermarket Lower Unit Seal Kit is intended for selected Johnson and Evinrude 85, 100, and 125 HP 2-stroke outboard models from 1971–1972 that use a large propeller shaft. The kit provides seals, gaskets, and O-rings for lower-unit and gearcase service, helping protect against water intrusion and gear-oil leaks when correctly installed.

This kit is listed as an aftermarket replacement for Sierra 18-2691, GLM 87611, and Mallory 9-74114. These numbers are aftermarket reference numbers; they should be used together with the complete engine model, year, and large-prop-shaft configuration to confirm suitability.

• Designed as a direct replacement service kit for the specified applications.
• For compatible models requiring lower-unit seals for a large propeller shaft.
• Includes the seal, O-ring, and gasket components needed for the listed lower-unit service application.

Part Number Matrix

Use the following aftermarket reference matrix together with your complete engine model and year. Do not order from a part number alone.

Engine & Model Compatibility

Confirm your exact engine model, model year, horsepower, 2-stroke configuration, and propeller-shaft size before ordering.

For Johnson and Evinrude owners, match the full model number and year to the table below. This kit is intended only for the listed applications equipped with a large propeller shaft. Horsepower alone is not sufficient to establish compatibility.

Technical Specifications

Product Type

Lower-unit and gearcase seal kit

Application

Selected Johnson/Evinrude 85, 100, and 125 HP 2-stroke outboards from 1971–1972

Propeller Shaft

Large propeller shaft applications

Installation

Direct replacement service installation

Product Status

Aftermarket replacement, not an OEM component

What’s in the Box

• Oil seals
• O-rings
• Gaskets

Installation Notes

1. Drain the old gearcase lubricant completely from the lower unit.
2. Remove the propeller assembly and unbolt the lower unit from the outboard’s leg.
3. Disassemble the gearcase as required to access the driveshaft and propeller-shaft carriers. Carefully remove the old seals, O-rings, and gaskets without scratching sealing surfaces.
4. Thoroughly clean all component surfaces of old adhesive, corrosion, and debris.
5. Lightly lubricate the new seals and O-rings with suitable marine grease before carefully pressing them into place with the appropriate seal driver.
6. Reassemble the gearcase components and tighten fasteners according to the engine manufacturer’s specified torque sequence and values.
7. Before reinstalling the unit, perform a suitable pressure and vacuum test to confirm that the seals are seated correctly and the gearcase has no leaks. Follow the manufacturer’s service procedure for the correct test pressure.
8. Refill the lower unit with the correct grade and amount of marine gear lubricant. Reinstall the lower unit and check for leaks after the first use.

Important: Lower-unit disassembly and pressure/vacuum testing require appropriate tools and service knowledge. If you are not equipped to complete the work safely, use a qualified marine technician.

Troubleshooting & FAQ

Safety & Important Information

• Verify the complete engine model, year, lower-unit configuration, and propeller-shaft size before ordering.
• Compare the original components and sealing surfaces with the kit before installation.
• This is an aftermarket replacement, not an OEM component.
• Use proper lifting, blocking, lubrication, torque, and pressure-testing procedures.
• Professional installation is recommended for safe and reliable service.

About Sea Sierra

• Pro-Grade Standards — We supply marine replacement parts selected for dependable service in real-world applications.
• Global Fulfillment — Shipping availability and delivery estimates are provided at checkout.
• Manufacturer-Direct Value — Practical replacement parts at competitive pricing.