Lower Unit Seal Kit – Fits Johnson/Evinrude 25-50 HP 2-Stroke (Replaces 433550, 18-2694)

Lower Unit Seal Kit – Fits Johnson/Evinrude 25-50 HP 2-Stroke (Replaces 433550, 18-2694)

This aftermarket lower unit seal kit is designed for Johnson/Evinrude 2-stroke outboard engines, including 25 HP (1990–1995, D suffix only), 40 HP (1989 & Up), 48 HP (1989–1996), and 50 HP (1989 & Up) models. It provides a complete solution for rebuilding and resealing your gearcase to prevent water intrusion and oil leaks.

This kit serves as a direct replacement for Johnson/Evinrude part numbers 433550, 0433550, and 777551, as well as Sierra 18-2694, GLM 87614, and Mallory 9-74104.

• Installation Type: Direct OEM-style replacement for a precise fit.
• Comprehensive Kit: Includes all necessary seals, gaskets, and O-rings for a complete lower unit rebuild.
• Durable Materials: Constructed from a mix of high-quality rubber, metal, and synthetic materials to meet or exceed original specifications.

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 comprehensive kit includes the following components:

• 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) - Prop Shaft Seal
• 1 x Oil seal (342786)
• 1 x Oil seal (342887) - Driveshaft Seal
• 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

1. Prepare the Lower Unit: Safely secure the engine and place a container under the lower unit to catch old gear lube. Remove the drain and vent plugs to empty the fluid completely.
2. Remove the Lower Unit: Disconnect the shift linkage (if applicable) and remove the bolts securing the lower unit to the engine's midsection. Carefully lower it away from the engine.
3. Disassemble the Gearcase: Following your specific service manual, remove the propeller, bearing carrier, driveshaft, and prop shaft assemblies to access the old seals.
4. Remove Old Seals: Carefully pry out the old oil seals, O-rings, and gaskets. Take care not to scratch or damage the metal sealing surfaces.
5. Clean Components: Thoroughly clean all parts and sealing surfaces with a suitable solvent, removing any old sealant, corrosion, or debris.
6. Install New Seals: Lightly coat the new seals and O-rings with marine grease. Use an appropriate seal driver or socket to press the new seals into place evenly and without damage.
7. Reassemble Components: Reinstall the driveshaft, prop shaft, and bearing carrier assemblies according to the manual, ensuring all components are properly seated.
8. Reattach Lower Unit: Guide the lower unit back into position, ensuring the driveshaft splines and water tube align. Re-engage the shift linkage and tighten the mounting bolts to the specified torque.
9. Refill Gear Lube: Fill the gearcase with new marine gear lubricant through the bottom drain hole until it flows out of the upper vent hole. Reinstall and tighten both plugs with new gaskets.
10. Final Check: Rotate the prop shaft to ensure smooth operation and check for any immediate signs of leaks.

Troubleshooting & FAQ

How do I confirm this fits my engine?
This kit is designed for specific Johnson/Evinrude 2-stroke models and years (25, 40, 48, and 50 HP). Please check the "Compatible Engine Models" table and cross-reference your engine's model and year. Verifying your engine's original part number against the "Part Number Cross-Reference" table is the most reliable method.

What are common signs that my lower unit seals are failing?
The most common indicator is "milky" or creamy-looking gear lube, which signifies water contamination. You may also notice gear oil leaking from the propeller shaft area or around the drain plugs. Grinding noises or difficulty shifting can also be symptoms of internal damage caused by failed seals.

How often should I replace the lower unit seals?
There is no fixed replacement interval. Seals should be inspected annually when you change your gear lube. We recommend replacing the full seal kit as a preventative measure every few years, or immediately if you notice any signs of leaks or water intrusion.

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.