Lower Unit Seal Kit – Fits Mercury/Mariner 9.9-25HP Outboards (Replaces 26-85090A2, 18-2624)

Lower Unit Seal Kit – Fits Mercury/Mariner 9.9-25HP Outboards (Replaces 26-85090A2, 18-2624)

This lower unit seal kit is designed for a wide range of Mercury and Mariner 9.9 HP to 25 HP outboard engines, including both 2-stroke and 4-stroke models. It provides the necessary components to restore the integrity of your lower gearcase, preventing water intrusion and oil leaks.

This kit serves as a direct replacement for Mercury part number 26-85090A2 and aftermarket part numbers Sierra 18-2624 and SeaSierra 18-2624, ensuring compatibility and a precise fit.

• Installation Method: Direct replacement for a seamless fit.
• Comprehensive Kit: Includes the essential seals, gaskets, and O-rings for a complete lower unit service.
• Durable Materials: Constructed from high-quality, reinforced rubber to withstand the harsh marine environment.

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 package includes: 1 x Lower Unit Seal Kit (Replaces 26-85090A2 / 18-2624).

The kit typically contains:

• Multiple seals
• O-rings
• Gaskets
• Necessary hardware for a complete lower unit seal replacement.

Installation Guide

1. Prepare the Lower Unit: Position the outboard securely and place a drain pan under the gearcase.
2. Drain Gear Lube: Remove the upper and lower gear lube drain screws and allow all oil to drain completely.
3. Remove Propeller: Straighten the cotter pin, remove the propeller nut, and slide the propeller assembly off the shaft.
4. Detach Lower Unit: Remove the bolts securing the lower unit to the engine's upper housing.
5. Disassemble Bearing Carrier: Access and remove the bearing carrier housing to expose the seals on the propeller shaft.
6. Replace Seals: Carefully remove the old seals and O-rings, taking note of their orientation. Clean the housing surfaces thoroughly.
7. Install New Seals: Lubricate the new seals with marine grease and press them into place using an appropriate seal driver.
8. Reassemble Components: Reinstall the bearing carrier, ensuring all components are torqued to manufacturer specifications.
9. Reattach Lower Unit: Mount the lower unit back onto the engine housing.
10. Refill Gear Lube: Fill the gearcase with fresh marine gear lubricant from the bottom screw hole until it flows out of the top hole. Reinstall both screws with new gaskets.

Troubleshooting & FAQ

Q: How do I confirm this kit will fit my specific engine model?

A: The surest method is to match your existing part number to the ones listed in our cross-reference table: Mercury 26-85090A2 or Sierra 18-2624. You can also consult the Compatible Engine Models table and use the provided Mercury serial number guide to verify your engine series.

Q: What are the common signs that my lower unit seals are failing?

A: The most common sign is "milky" or creamy-looking gear lube, which indicates water has mixed with the oil. You may also notice gear oil leaking from the propeller shaft area or around the drain/fill screws.

Q: How often should I replace the lower unit seals?

A: There is no fixed replacement interval. Seals should be inspected annually when you change your gear lube. It is good practice to replace them if you see any signs of leakage, or as preventative maintenance every 3-5 years, especially in saltwater environments.

Q: OEM vs. Aftermarket?

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.