Lower Unit Gearcase Seal Kit – Fits Johnson/Evinrude 40HP, 48HP & 50HP 2-Stroke Outboards (Replaces 433550, 0777551)

Lower Unit Gearcase Seal Kit – Fits Johnson/Evinrude 40HP, 48HP & 50HP 2-Stroke Outboards

This comprehensive lower unit gearcase seal kit is designed for Johnson/Evinrude 40HP, 48HP, and 50HP 2-stroke outboard engines from 1989 to 2005. It provides all the necessary components to service your lower unit and prevent water intrusion or oil leaks.

This kit is a direct replacement for OEM part numbers 433550 and 0777551, as well as several other aftermarket equivalents, including Sierra 18-2694, GLM 87614, and Mallory 9-74104.

• Complete Service Kit: Includes all necessary seals, O-rings, and gaskets for a full lower unit reseal.
• Direct Replacement: Engineered to match OEM fit and function for a hassle-free installation.
• Durable Materials: Constructed from high-quality rubber and metal components to ensure a long-lasting, reliable seal.

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

• 1 x Gearcase Seal Kit (contains approximately 20 pieces)
• 1 x Installation Instructions

The kit typically includes:

• 1 x O-Ring (305270)
• 1 x O-Ring (338522)
• 1 x Wear plate gasket (336530)
• 1 x O-Ring (310327/910582)
• 1 x O-Ring (317178)
• 1 x O-Ring (553126)
• 1 x O-Ring (318372)
• 1 x Seal (333758)
• 1 x Oil seal (321466)
• 1 x Oil seal (332205)
• 1 x Oil seal (342786)
• 1 x Oil seal (342887)
• 1 x Seal (315748/341732)
• 1 x Gasket (311598)
• 1 x Drain plug Screw (318544)
• 1 x Housing Seal ring (324981)
• 1 x Drain plug (309243)
• 1 x O-Ring (336982)
• 1 x Retaining screw (324852)
• 1 x Washer seal ring (332584)

Installation Guide

Follow these general steps for installation. For detailed instructions specific to your engine model, please consult your official service manual.

1. Drain Oil: Position a drain pan under the lower unit and remove the upper and lower gearcase drain/fill screws to drain the gear lube completely.
2. Remove Lower Unit: Remove the propeller assembly. Disconnect the shift linkage and remove the bolts securing the lower unit to the engine's midsection, then carefully lower it.
3. Disassemble Components: Disassemble the gearcase housing, propshaft bearing housing, and driveshaft components to access the old seals. Keep all parts organized.
4. Remove Old Seals: Carefully pry out the old oil seals, O-rings, and gaskets from the housing, driveshaft, and propshaft areas. Take care not to scratch the metal surfaces.
5. Clean Surfaces: Thoroughly clean all sealing surfaces, removing any old gasket material, sealant, or corrosion. A clean surface is critical for a good seal.
6. Install New Seals: Lubricate the new seals and O-rings with a light coat of marine grease. Carefully press the new seals into place using an appropriate seal driver or socket, ensuring they are seated evenly.
7. Reassemble: Reassemble the gearcase components in the reverse order of disassembly, making sure to install all new gaskets and O-rings from the kit.
8. Reinstall & Refill: Reinstall the lower unit onto the outboard, reconnect the shift linkage, and torque all bolts to the manufacturer's specification. Refill the gearcase with fresh marine gear lube until it flows from the upper vent hole, then reinstall both screw plugs.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my specific Johnson/Evinrude engine?

A: This kit is designed for most Johnson/Evinrude 40HP, 48HP, and 50HP 2-stroke outboards made from 1989 and later, along with some 1990-1995 25HP models (D suffix only). To be certain, please compare your engine's model and year against the "Compatible Engine Models" chart. You can also cross-reference your existing part number with the numbers in our "Part Number Cross-Reference" table.

Q: What are the signs that my gearcase seals are failing?

A: The most common sign of a failed seal is milky or foamy gear lube, which indicates water has mixed with the oil. Other symptoms include visible oil leaks around the propeller shaft or the drain and vent screws, or finding metal shavings on the magnetic drain plug, which can signal internal damage caused by water contamination.

Q: Is this kit identical to the original BRP/OMC kit?

A: This is an aftermarket kit engineered to meet OEM specifications for fit and performance. It directly replaces OEM part 433550 and contains all the essential seals, gaskets, and O-rings for a standard lower unit service on the listed engines. While component contents are comparable, they may not be 100% identical in count or material to the original manufacturer's kit.

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.