26-43035A4 Lower Unit Gearcase Seal Kit for Mercury Force | JLM Marine

Lower Unit Gearcase Seal Kit – Fits Mercury & Force 30-125 HP Outboards | OEM 26-43035A4

This comprehensive gearcase seal kit is designed for Mercury Mariner and Force outboard lower units, covering a wide range of models from 30 HP to 125 HP. Whether you're performing routine maintenance or a complete lower unit rebuild, this kit provides all the essential seals, gaskets, and O-rings needed to ensure a proper seal and prevent water intrusion or gear oil leaks.

This aftermarket replacement directly replaces OEM part numbers 26-43035A1, 26-43035A2, 26-43035A3, 26-43035A4, and Sierra 18-2626, ensuring broad compatibility across multiple Mercury and Force models from the late 1980s through 2007.

• Complete seal and gasket set for lower unit service and rebuild
• Includes drive shaft seals, impeller gaskets, O-rings, and water tube seals
• Fits Mercury 30-125 HP and Force 75-120 HP outboards

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

This complete seal kit includes the following components for a thorough lower unit service:

• Impeller Face Plate Gasket (27-43033)
• Impeller Gasket (27-43047)
• Impeller Gasket (27-43034)
• Impeller Gasket (27-817277)
• Drain Screw Gasket (12-19183)
• O-Ring (25-45710)
• O-Ring (25-805726)
• O-Ring (25-47254)
• Oil Seal (26-76384)
• Oil Seal (26-70081)
• Water Tube Seal (2 pieces)
• Insulator Bushing (23-43045)
• Drive Shaft Oil Seal (26-43036)

Installation Guide

1. Disconnect the battery and remove the lower unit from the outboard following your engine's service manual procedures.
2. Drain all gear oil completely and clean the exterior of the lower unit housing thoroughly.
3. Remove the water pump assembly and disassemble the lower unit gearcase to access all seal locations.
4. Carefully remove old seals, gaskets, and O-rings using appropriate seal removal tools; avoid scratching seal bore surfaces.
5. Clean all seal bores, mating surfaces, and grooves with a non-abrasive cleaner and inspect for corrosion or damage.
6. Lubricate new seals with marine-grade grease or gear oil before installation to prevent tearing.
7. Install the new drive shaft oil seal (26-43036) ensuring the lip faces inward toward the gear oil.
8. Replace all impeller gaskets, O-rings, and water tube seals as outlined in the package contents.
9. Reassemble the lower unit gearcase, torquing all fasteners to manufacturer specifications.
10. Install a new drain screw gasket and refill the lower unit with the correct grade and quantity of marine gear oil.
11. Reinstall the lower unit to the outboard and reconnect all shift linkage and cooling water connections.
12. Test the engine in a tank or on the water, checking for leaks and proper shifting operation.

Troubleshooting & FAQ

Q: How do I know if this seal kit fits my specific Mercury or Force engine?
A: Cross-reference your engine's horsepower, model year, and serial number with the compatibility table above. If your engine is listed and the OEM part number matches 26-43035A1 through A4, this kit will fit. You can also check Mercury's parts diagrams using the links provided.

Q: What are the signs that my lower unit seals need replacement?
A: Common symptoms include milky or contaminated gear oil (indicating water intrusion), visible oil leaks around the propeller shaft or lower unit seams, unusual noise or vibration from the gearcase, and difficulty shifting gears.

Q: How often should I replace the lower unit seals?
A: Mercury recommends inspecting seals during routine lower unit service (typically every 100 hours or annually). Replace seals if you notice any leaks, during water pump replacement, or anytime the lower unit is disassembled for repair.

Q: Can I reuse the old gaskets if they look intact?
A: No, always replace all gaskets and seals during lower unit service. Even if they appear undamaged, they compress and conform to surfaces during initial installation and will not seal properly if reused.

Q: What's the difference between OEM and aftermarket seal kits?
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.