Lower Unit Gearcase Seal Kit – Fits Johnson/Evinrude 20-35 HP (Replaces 396351, 87680, 18-2658)

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

This complete lower unit gearcase seal kit is designed for Johnson/Evinrude 20, 25, 30, and 35 HP 2-stroke outboard engines from 1977 to 2005. It provides a direct replacement solution for maintaining and repairing your engine's lower unit.

This kit serves as a direct replacement for Johnson/Evinrude OEM part 396351 / 0396351, Sierra 18-2658, GLM 87680, and Mallory 9-74101.

• Installation Type: Direct replacement for a seamless fit.
• Comprehensive Kit: Includes all necessary gaskets, o-rings, and seals for a standard gearcase service.
• Engine Compatibility: Precisely manufactured for specific Johnson/Evinrude 2-stroke models.

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 the following components:

• 1 x Impeller Plate Gasket
• 1 x Shift Rod Washer
• 2 x Oil Seals (Driveshaft)
• 1 x Oil Seal
• 1 x Oil Seal
• 1 x Oil Seal
• 1 x Oil Seal
• 1 x Rubber Seal
• 2 x Drain/Fill Plug Washers
• 1 x O-Ring
• 2 x O-Ring
• 1 x O-Ring
• 3 x O-Ring
• 2 x O-Ring
• 1 x O-Ring
• 1 x O-Ring

Note: The exact quantity of each type of seal may vary slightly between aftermarket kits to cover a wide range of models. You may have leftover parts after installation.

Installation Guide

Follow these general steps for installation. Refer to your engine's official service manual for detailed instructions.

1. Drain Gear Oil: Position a drain pan under the lower unit and remove the upper (vent) and lower (drain) screws to drain the gear lube completely.
2. Remove Propeller: Straighten the cotter pin, remove the castle nut, and slide the propeller and thrust washer off the shaft.
3. Remove Lower Unit: Disconnect the shift linkage (if applicable) and remove the bolts securing the gearcase to the engine's midsection.
4. Disassemble and Inspect: Carefully disassemble the gearcase, including the water pump housing and bearing carriers, noting the orientation of all parts.
5. Replace Seals: Remove the old seals and o-rings from the driveshaft and propeller shaft carriers. Clean the seal surfaces and press the new seals into place squarely.
6. Reassemble: Reassemble the gearcase components in reverse order, ensuring all parts are correctly seated and torqued to factory specifications.
7. Refill with Lube: With the gearcase reinstalled, inject new lower unit lube into the bottom drain hole until it flows out of the top vent hole. Reinstall the vent and drain screw with new washers.

Troubleshooting & FAQ

How do I confirm this seal kit fits my engine?
First, check the Part Number Cross-Reference table to see if your old part number is listed. Second, review the Compatible Engine Models list to ensure your specific HP, year, and model are included. For Johnson/Evinrude engines, using the serial number guide can help confirm your model year accurately.

What are the signs that my gearcase seals are failing?
The most common sign is milky or creamy-looking gear lube, which indicates water intrusion. You might also notice gear oil leaking from around the propeller shaft or from the "telltale" water stream. A failed pressure/vacuum test during service also confirms a leak.

Are there extra seals in this kit?
Yes, it is common to have leftover seals or o-rings. This kit is designed to cover multiple engine years and models, which may have slight variations. Use only the parts that match the ones you removed from your specific unit.

OEM vs. Aftermarket?
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.

How fast do you ship and how much does it cost?
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.

What is your warranty and return policy?
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.