Lower Gearcase Seal Kit – Fits MerCruiser Alpha One Gen 2 Sterndrives (Replaces 26-816575A3, 26-816575A1)

Lower Gearcase Seal Kit – Fits MerCruiser Alpha One Gen 2 Sterndrives (Replaces 26-816575A3, 26-816575A1)

This lower gearcase seal kit is designed for MerCruiser Alpha One Gen 2 sterndrives (1991–present) with serial numbers 0D469859 and later. It provides a comprehensive solution for servicing and resealing the lower drive unit to prevent water intrusion and oil leaks.

This kit serves as a direct replacement for MerCruiser OEM part numbers 26-816575A3 and 26-816575A1. It also cross-references with Sierra 18-2646-1, GLM 87511, and Mallory 9-74206.

• Engineered as a direct replacement for a perfect fit and reliable function.
• Prevents water from entering and oil from leaking out of the gearcase.
• Includes all the necessary gaskets, seals, and O-rings for a complete lower unit service.

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

• 1 x Carrier Seal (821759A2)
• 1 x Impeller Gasket (27-43033-1)
• 1 x Seal Ring (26-45577)
• 1 x Impeller Gasket (27-817277)
• 1 x Oil Seal (26-8164641)
• 1 x Oil Seal (26-12224)
• 1 x Face Seal (8M2014338)
• 2 x Drain Screw Gasket (26-830749)
• Various O-Rings

Installation Guide

1. Position the sterndrive in the full-down position and place a drain pan under the lower unit. Remove the upper and lower drain/fill screws and drain the gear lube completely.
2. Remove the propeller assembly.
3. Unbolt and carefully separate the lower gearcase unit from the upper housing. Be prepared to support its weight.
4. With the lower unit on a workbench, remove the water pump housing and impeller assembly to access the upper seals.
5. Remove the bearing carrier to access the propeller shaft seals. This may require a specialized puller tool.
6. Carefully remove all old seals, O-rings, and gaskets from the housing, driveshaft, and bearing carrier. Clean all sealing surfaces thoroughly, removing any old sealant or corrosion.
7. Install the new seals and O-rings into their respective locations. Ensure seals are seated correctly and facing the proper direction to prevent leaks.
8. Reinstall the bearing carrier and water pump assembly, using the new gaskets provided in the kit.
9. Reattach the lower gearcase unit to the upper housing, ensuring the driveshaft, shift shaft, and water tube align correctly. Torque bolts to manufacturer specifications.
10. Reinstall the propeller.
11. Refill the gearcase with new, high-quality marine gear lube through the bottom hole until it flows from the top hole. Reinstall the vent and fill screw gaskets and screws.

Troubleshooting & FAQ

How do I confirm this kit fits my engine?
This kit is specifically for MerCruiser Alpha One Gen 2 sterndrives manufactured from 1991 to the present. The most important check is your serial number; it must be 0D469859 or later. Do not use this kit if your drive is a Gen 1 or has a lower serial number.

What are the signs my gearcase seals are failing?
The most common sign is milky, light-colored gear lube, which indicates water has mixed with the oil. You may also notice gear oil leaking from the propeller shaft area or from the drain screw seals.

How often should I replace the lower unit seals?
It is recommended to inspect your gear lube for water after every season. Seals should be replaced as part of regular maintenance every few years, or immediately if you detect a leak or water intrusion. Many technicians replace the water pump impeller and lower unit seals at the same time.

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.