Lower Unit Gearcase Seal Kit – Fits Mercury/Mariner 30-125 HP (Replaces 26-43035A4)

Lower Unit Gearcase Seal Kit – Fits Mercury/Mariner 30-125 HP (Replaces 26-43035A4)

This gearcase seal kit is designed for Mercury and Mariner outboard engines with horsepower ratings from 30 to 125 HP. It fits both 2-stroke and 4-stroke models manufactured between 1991 and 2010.

Compatible with lower units featuring either a 3-jaw or 6-jaw reverse clutch, this kit serves as a direct replacement for a range of Mercury and Mariner part numbers, as well as certain Sierra, GLM, and Mallory equivalents.

• Includes various seals, gaskets, O-rings, and related components necessary for lower unit gearcase maintenance.
• Suitable for both 2-stroke and 4-stroke Mercury/Mariner engines across multiple models and years.
• Installation is a direct replacement process for ease of maintenance.

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 Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

• Various oil seals
• Various gaskets
• Various O-rings
• Drain screw gasket(s)
• Water line seal(s)
• Impeller gasket(s)
• Washer(s)
• Insulator bushing(s)
• Drive shaft oil seal(s)

Installation Guide

1. Ensure the engine is turned off and secured before beginning installation.
2. Remove the lower unit from the outboard motor according to manufacturer instructions.
3. Drain all fluids from the gearcase.
4. Disassemble the lower unit gearcase housing carefully, noting placement of components.
5. Remove old seals, gaskets, and O-rings from the gearcase and drive shaft areas.
6. Clean all mating surfaces thoroughly to ensure proper sealing.
7. Install the new seals, gaskets, and O-rings included in the kit as per their respective locations.
8. Replace the drain screw gasket and water line seals as necessary.
9. Reassemble the gearcase housing and ensure all components are seated properly.
10. Reinstall the lower unit onto the outboard motor securely.
11. Refill gearcase with the appropriate lubricant as specified by the engine manufacturer.
12. Test operation carefully to verify proper installation and no leaks.

Troubleshooting & FAQ

• How do I confirm this fits my engine? Check your engine’s model and year against the compatibility table above, and verify your engine’s serial number using the Mercury Serial Number Guide linked.
• What are the differences compared to OEM parts? This is an aftermarket replacement built to OEM specifications using comparable-grade materials; it is not an OEM component but meets similar standards.
• How often should I replace the gearcase seal kit? Replacement intervals vary based on usage and conditions, but inspect seals regularly and replace if you notice leaks or damage.
• What are common signs of a failing gearcase seal? Look for water intrusion in the lower unit, oil leaks, or unusual noises during operation.
• 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.