Upper Gear Housing Seal Kit – Fits MerCruiser R, MR & Alpha One Gen I Drives (Replaces Mercury 26-32511A1, Sierra 18-2648)
Upper Gear Housing Seal Kit – Fits MerCruiser R, MR & Alpha One Gen I Drives (Replaces Mercury 26-32511A1, Sierra 18-2648) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Upper Gear Housing Seal Kit – Fits MerCruiser R, MR & Alpha One...
Product Details
This Upper Gear Housing Seal Kit provides all necessary components to reseal the upper unit on MerCruiser #1, R, MR, and Alpha One Gen I stern drives manufactured from 1964–1991 (serial numbers 1684188 through D469858). It ensures a reliable, leak-free seal to protect your drive's internal components.
This kit serves as a direct replacement for Mercury part numbers 26-32511A1, 26-32511A3, and 26-32511B1, as well as Sierra 18-2648, GLM 87500, and Mallory 9-74303.
- Engineered for direct-fit installation, requiring no modifications.
- Some aftermarket versions may include upgraded double-lip seals or stainless steel components for enhanced durability.
- Restores seals to prevent water intrusion and oil leaks, extending gear life.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 26-32511A1 |
| Mercury | 26-32511A3 |
| Mercury | 26-32511B1 |
| Sierra | 18-2648 |
| GLM | 87500 |
| Mallory | 9-74303 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This kit is designed for a wide range of MerCruiser stern drive models. Verify your serial number falls within the specified range to ensure correct fitment.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | #1 / Model 1 | Various | 4-Stroke | 1964–1966 | 26-32511A1 | Serial #1684188-2065189 |
| MerCruiser | #1A, 1B, 1C & EZ Shift | Various | 4-Stroke | 1964–1966 | 26-32511A1 | Serial #1684188-2065189 |
| MerCruiser | 120 | 120 | 4-Stroke | 1967–1982 | 26-32511A1 | Serial #2062141-6225576 |
| MerCruiser | 140 | 140 | 4-Stroke | 1967–1982 | 26-32511A1 | Serial #2062141-6225576 |
| MerCruiser | 160/165 | 160/165 | 4-Stroke | 1967–1977 | 26-32511A1 | Serial #2065190 and up |
| MerCruiser | 470 | 170/190 | 4-Stroke | 1976–1982 | 26-32511A1 | Serial #4208730-6225576 |
| MerCruiser | 485 | 185/200 | 4-Stroke | 1976–1982 | 26-32511A1 | Serial #4208730-6225576 |
| MerCruiser | 888 | 200/240 | 4-Stroke | 1971–1977 | 26-32511A1 | Serial #3106717 and up |
| MerCruiser | 898/228/250/260 | Various | 4-Stroke | 1977–1982 | 26-32511A1 | Serial #4782330-4898729 |
| MerCruiser | R/MR | Various | 4-Stroke | 1983–1991 | 26-32511A1 | Serial #6225577 and up |
| MerCruiser | Alpha One | Various | 4-Stroke | 1983–1991 | 26-32511A1 | Serial #6225577 and up |
| MerCruiser | Alpha One SS | Various | 4-Stroke | 1986–1989 | 26-32511A1 | Serial #0A545004 and up |
| MerCruiser | SSM II/III/IV/V | Various | 4-Stroke | 1982–1995 | 26-32511A1 |
Technical Specs
- Product Type
- Upper Unit Gear Housing Seal Kit
- Installation
- Direct replacement
- Housing Material
- Rubber/Synthetic components
- Housing Color
- Black
- Warranty
- Varies by manufacturer
- Other Technical Attributes
- Contains stainless steel OD seals in some aftermarket versions
What’s in the Box
- 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 Notes
- Drain the gear lube from the stern drive completely.
- Carefully remove the upper gear housing assembly from the drive.
- Disassemble the unit as needed to access the old seals, gaskets, and O-rings. Note the orientation and position of each component as you remove it.
- Thoroughly clean all mating surfaces, removing any old sealant or corrosion.
- Install the new seals, gaskets, and O-rings from the kit. Lightly lubricate rubber components with a suitable marine grease before installation.
- Reassemble the upper gear housing and torque all fasteners to the manufacturer's specifications.
- Refill the drive with fresh, high-quality marine gear lube and check thoroughly for any leaks before operation.
Troubleshooting & FAQ
How do I know if this seal kit fits my MerCruiser drive?
This kit is designed for MerCruiser R, MR, and Alpha One Gen I drives from 1964–1991. The most reliable way to confirm fitment is to match your drive's serial number to the ranges listed in the compatibility table (1684188–D469858). Do not rely on model year alone.
What are the signs of a failing upper unit seal?
The most common symptom is milky, grey, or cloudy gear lube, which indicates water has contaminated the oil. Other signs include visible oil leaks around the upper housing or a noticeable drop in the gear lube level.
Is this kit an upgrade over the original OEM parts?
Some aftermarket kits provide seals made from modern materials that may offer improved durability. For instance, some seals in this kit might be a double-lip design or feature stainless steel components, which can provide a better seal and longer service life than the original single-lip designs.
How often should these seals be replaced?
Preventative replacement is recommended any time the gear housing is disassembled for service. Otherwise, they should be replaced immediately if you detect any signs of leakage or water intrusion. Regular inspection of your gear lube is key to catching failures early.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns?
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
Payment & Security
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