Gearcase Seal Kit – Fits Johnson/Evinrude 40-75 HP Outboards (Replaces 5000309, 396349, 777558)

Gearcase Seal Kit – Fits Johnson/Evinrude 40-75 HP Outboards (Replaces 5000309, 396349, 777558)

This gearcase seal kit is designed for a wide range of Johnson and Evinrude 40-75 HP, 2-stroke outboard engines from 1978 to 1999. It is specifically intended for large case models featuring a 20" transom and 3 water intake holes per side, ensuring a precise fit for these configurations.

It serves as a direct replacement for multiple OEM and aftermarket part numbers, including Johnson/Evinrude 5000309, 396349, and 0777558; Sierra 18-8383 and 18-2660; GLM 87601; and Mallory 9-74103.

• Installation Location: Lower Unit/Gearcase
• Engine Compatibility: 2-Stroke Gasoline Engines
• Specific Application: For large case models with 20" transom and 3 water intake holes per side

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

Installation Guide

Professional installation is recommended. The following is a general guide:

1. Drain Lubricant: Begin by completely draining the old lubricant from the gearcase.
2. Remove Lower Unit: Detach the propeller assembly and remove the lower unit from the outboard engine.
3. Disassemble: Carefully disassemble the lower unit to access the driveshaft and propeller shaft seals. Keep all components in order.
4. Remove Old Seals: Extract the old seals, O-rings, and gaskets, taking care not to scratch any metal surfaces.
5. Clean Surfaces: Thoroughly clean all sealing surfaces to ensure they are free of debris and old adhesive.
6. Install New Seals: Install the new seals, gaskets, and O-rings from the kit. Ensure each part is properly seated in its correct location and orientation.
7. Lubricate: Apply a light coat of marine grease to the new seals to prevent damage during reassembly and aid in sealing.
8. Reassemble: Reassemble the gearcase components in the reverse order of disassembly, torquing bolts to manufacturer specifications.
9. Reinstall Unit: Mount the lower unit back onto the outboard.
10. Refill Lubricant: Fill the gearcase with the manufacturer-recommended gear lubricant to the proper level.
11. Check for Leaks: Before operating the boat, check for any signs of oil or water leaks around the newly sealed areas.

Troubleshooting & FAQ

How do I confirm this kit fits my specific engine model?
This kit is designed for Johnson/Evinrude 40–75 HP, 2-stroke outboard engines (1978–1999) that are large case models with a 20" transom and have 3 water intake holes on each side. Please refer to the compatible models table and cross-reference your engine's model number and year.

What are the common signs that my gearcase seals need replacement?
Common signs include milky or water-contaminated gear lube (visible during a drain), oil leaking from the propeller shaft area, or a loss of gearcase pressure. A visual inspection for leaks around the prop shaft and driveshaft is also a key indicator.

How often should I replace the gearcase seals?
It is good practice to inspect your gear lube annually or every 100 hours of use. We recommend replacing the seals whenever the lower unit is being serviced for other reasons (like a water pump replacement) or if you notice any signs of leakage 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.