Gearcase Lower Unit Seal Kit – Fits Johnson/Evinrude 40-75 HP (Replaces 5000309, 396349, Sierra 18-8383)

Gearcase Lower Unit Seal Kit – Fits Johnson/Evinrude 40-75 HP

This gearcase lower unit seal kit is designed for Johnson/Evinrude 2-stroke outboard engines, 40-75 HP large case models (1998 and later) with a 20" transom length. It is specifically for models featuring 3 water intake holes per side of the gearcase.

It serves as a direct replacement for multiple OEM and aftermarket part numbers, including Johnson/Evinrude 5000309, 396349, 777558; Sierra 18-8383, 18-2660; GLM 87601; and Mallory 9-74103.

• Compatible with 2-Stroke gasoline engines.
• Includes the essential seals, O-rings, and gaskets for a complete lower unit reseal.
• Suitable for both DIY and professional installation.

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

• Prop Shaft Seal (OEM 330137)
• Drive Shaft Oil Seal(s) (OEM 341280)
• Drive Shaft to Crankcase O-ring (OEM 310585)
• Prop Shaft Carrier O-ring (OEM 313446)
• Shift Cover O-ring (OEM 318372)
• Shift Cover Gasket (OEM 324670)
• Water Pump Gasket (OEM 338484)
• Pitot Hole Plug Sealing Washer (OEM 437330)
• Drain Plug and Gasket (OEM 318544)
• Prop Shaft Carrier Screw and Seal (OEM 316563)

Installation Guide

Follow these general steps to replace the lower unit seals. Refer to your engine's service manual for detailed instructions.

1. Drain the oil: Start by completely draining the gearcase oil.
2. Remove lower unit: Detach the lower unit from the outboard engine's driveshaft housing.
3. Disassemble: Carefully disassemble the gearcase to access the water pump, bearing carriers, and shafts.
4. Remove old seals: Extract the old propeller shaft seals, driveshaft seals, O-rings, and gaskets.
5. Clean surfaces: Thoroughly clean all sealing surfaces and component housings, removing any old sealant or corrosion.
6. Install new seals: Lubricate the new seals with a light coat of marine grease and press them into place, ensuring they are perfectly seated.
7. Reassemble gearcase: Reinstall shafts, carriers, and the water pump assembly using the new gaskets and O-rings provided.
8. Reattach lower unit: Mount the lower unit back onto the engine.
9. Refill with lubricant: Fill the gearcase with the manufacturer-recommended lower unit lubricant to the proper level.
10. Check for leaks: Before operation, inspect the unit for any signs of oil or water leaks.

Troubleshooting & FAQ

How do I confirm this fits my engine?
This kit fits Johnson/Evinrude 40, 45, 50, 55, 60, 65, 70, and 75 HP 2-stroke "large case" models from 1998 and newer. Your gearcase must have 3 water intake holes per side and a 20" transom length. The best way to ensure a match is to cross-reference your existing part number with those listed, such as OEM 5000309 or 396349.

What are the signs of a failing gearcase seal?
Common signs include discovering milky, cream-colored gear lube (indicating water intrusion), visible oil leaks around the propeller shaft or under the water pump housing, or a persistent smell of gear oil after the engine has been tilted up.

Does this kit include everything for a full reseal?
Yes, it is a comprehensive kit containing the primary seals for the propeller shaft and driveshaft, as well as the necessary O-rings and gaskets for reassembly of the lower unit components like the bearing carrier and shift cover.

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.