Upper Gear Housing Seal Kit – Fits MerCruiser R, MR & Alpha One Gen I Drives (Replaces 26-32511A1, 18-2648)

Upper Gear Housing Seal Kit – Fits MerCruiser R, MR & Alpha One Gen I Drives

This comprehensive seal kit is designed for MerCruiser #1, R, MR, and Alpha One Gen I sterndrives manufactured from 1964 through 1991 (serial numbers 1684188 to D469858). It contains all the necessary gaskets, o-rings, and seals to service the upper gear housing unit, preventing water intrusion and oil leaks.

This kit is a direct replacement for multiple OEM and aftermarket part numbers, including Mercury 26-32511A1, 26-32511A3, 26-32511B1, Sierra 18-2648, GLM 87500, and Mallory 9-74303.

• Provides a complete solution for resealing the upper gearcase.
• Engineered as a direct, model-specific replacement for a reliable fit.
• Some included seals feature stainless steel OD construction for enhanced durability.

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 Upper Gear Housing Seal Kit containing:

• 1 x Grommet (26-38970)
• 1 x Gasket (27-55810-1)
• 2 x Gasket (12-19183-3)
• 1 x O-ring (25-55801)
• 1 x O-ring (25-32546)
• 1 x O-ring (25-25439)
• 1 x O-ring (25-70937)
• 1 x Oil Seal (26-32511)
• 1 x Oil Seal (26-823894)
• 1 x Oil Seal (26-96503-1)
• 1 x Seal (26-45577-1)
• 1 x Grommet (26-36557)

Installation Guide

1. Drain the gear lube completely from the sterndrive.
2. Separate the upper and lower units of the sterndrive assembly.
3. Carefully remove the upper gear housing cover to access the internal components.
4. Take photos of the old seals and their orientation before removal to use as a reference.
5. Use appropriate seal pullers or tools to carefully extract the old seals, gaskets, and o-rings.
6. Thoroughly clean all sealing surfaces, ensuring they are immaculate and free of old gasket material or corrosion.
7. Compare the new components from the kit with the old ones to confirm an exact match.
8. Install the new o-rings and gaskets onto the housing and cover.
9. Lightly lubricate the new oil seals with clean gear lube and press them into place using a seal driver.
10. Reassemble the gear housing, making sure to torque all fasteners to the manufacturer's specifications.
11. Rejoin the upper and lower units and refill the sterndrive with fresh, manufacturer-recommended gear lube.
12. After refilling, inspect carefully for any signs of leaks before operating the vessel.

Troubleshooting & FAQ

Q: How do I know if this seal kit will fit my sterndrive?

A: This kit is specifically designed for MerCruiser #1, R, MR, and Alpha One Gen I drives from 1964–1991. The most reliable way to confirm fitment is to check your drive's serial number; it should fall between 1684188 and D469858. You can also use the cross-reference table to match your existing part number.

Q: What are the signs that my upper gear housing seals are failing?

A: Common signs of seal failure include milky or water-contaminated gear lube (which looks like chocolate milk), a visible oil leak around the upper housing, or a persistent low gear lube level without an obvious external leak.

Q: Are these seals different from the original OEM ones?

A: Our seals are manufactured to meet or exceed OEM specifications for fit and function. Additionally, some versions in our kits feature upgrades like double-lip seals or stainless steel outer casings for improved durability and sealing performance compared to original single-lip designs.

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.