Gearcase Lower Unit Seal Kit – Fits Johnson/Evinrude 20-35 HP (Replaces 396351, 777559)

Gearcase Lower Unit Seal Kit – Fits Johnson/Evinrude 20-35 HP

This gearcase lower unit seal kit is designed for Johnson/Evinrude 20-35 HP 2-Stroke outboard motors manufactured between 1977 and 2005. It provides the necessary components to rebuild the lower unit and prevent water intrusion, ensuring the longevity and performance of your engine.

This kit is a direct replacement for multiple OEM and aftermarket part numbers, including Johnson/Evinrude 396351 and 777559, Sierra 18-2658, GLM 87680, Mallory 9-74101, and QuickMarine 5007987.

• Installation: Direct replacement for original parts.
• Compatibility: Fits specific 2-stroke Johnson/Evinrude models (20-35 HP).
• Function: Contains essential seals and gaskets to service the lower unit gearcase.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Johnson/Evinrude owners, here’s a guide to help you identify your engine’s serial/model: Johnson/Evinrude Serial Number Guide.

Technical Specifications

Package Contents

This kit includes all necessary seals, O-rings, and gaskets for rebuilding the lower unit gearcase. Note: While this kit is designed as a comprehensive replacement, specific component quantities are not enumerated. Please compare the kit contents with your existing parts before starting installation.

Installation Guide

1. Drain Oil: Begin by completely draining the old gearcase oil.
2. Remove Lower Unit: Detach the lower unit assembly from the outboard motor's main housing.
3. Access Seals: Disassemble the gearcase to access the driveshaft and propeller shaft areas where the seals are located.
4. Remove Old Seals: Carefully remove all old seals, O-rings, and gaskets. Take note of their position and orientation.
5. Clean Surfaces: Thoroughly clean all sealing surfaces to remove any old sealant, corrosion, or debris.
6. Lubricate New Seals: Apply a light coat of marine grease to the new seals and O-rings before installation to prevent damage.
7. Install New Components: Carefully press the new seals into place, ensuring they are fully seated and correctly oriented.
8. Reassemble: Reassemble the gearcase, making sure all components are torqued to manufacturer specifications.
9. Reinstall Unit: Mount the lower unit back onto the outboard motor.
10. Refill Oil: Fill the gearcase with the recommended type and quantity of fresh marine gear oil.
11. Check for Leaks: After refilling, check for any signs of oil leakage around the seals before operating the engine.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my engine?
A: This kit is specifically for Johnson/Evinrude 20-35 HP two-stroke outboards within the year ranges listed. The most reliable method is to cross-reference your engine's original part number with the provided list (396351, 777559) and consult the compatible models table.

Q: What are the symptoms of a failing gearcase seal?
A: The most common sign is milky, cloudy, or water-contaminated gear oil, which you can see when draining the lower unit. Other indicators include visible oil leaks around the propeller shaft or driveshaft housing.

Q: Some online reviews mention certain seals don't fit. What should I do?
A: Our kits are manufactured to meet or exceed OEM specifications for the listed models. However, due to running changes in production over the years, minor variations can exist. We strongly recommend comparing the new seals with your old ones before installation. If a part appears incorrect, do not force it. Contact our support team for assistance.

Q: OEM vs. Aftermarket?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.