Upper Unit Seal Kit – Fits MerCruiser Alpha One Gen 2 Sterndrives (Replaces 26-88397A1)
Upper Unit Seal Kit – Fits MerCruiser Alpha One Gen 2 Sterndrives (Replaces 26-88397A1) 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).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Upper Unit Seal Kit – Fits MerCruiser Alpha One Gen 2 Sterndrives (...
Product Details
This Upper Unit Seal Kit – Fits MerCruiser Alpha One Gen 2 Sterndrives (Replaces 26-88397A1) is specifically designed for MerCruiser Alpha One Generation 2 models from 1991 and newer. It contains the necessary components for servicing the seals in the upper driveshaft housing to prevent water intrusion and oil leaks.
It serves as a direct replacement for Sierra 18-2644 and Mercury 26-88397A1, offering a reliable alternative for maintenance and repair.
- For upper driveshaft housing seal service.
- Professional installation is recommended for optimal performance.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Sierra | 18-2644 |
| Mercury | 26-88397A1 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This kit is designed for MerCruiser Alpha One Gen 2 sterndrives.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | Alpha One Gen 2 | Various | 4-Stroke | 1991 and up | 26-88397A1 | Used with MSE |
Technical Specs
- Product Type
- Upper Unit Seal Kit
- Dimensions
- 7.5" L x 6.0" W x 0.5" H
- Weight
- 2.11 ounces (59.8 g)
- Other Technical Attributes
- For upper driveshaft housing seal service
What’s in the Box
- Gaskets and Seals for upper drive unit (equivalent to 26-88397A1)
Installation Notes
Professional installation is highly recommended to ensure correct alignment and sealing. Improper installation can lead to water entering the sterndrive, causing significant and costly damage to internal components.
Troubleshooting & FAQ
How do I know if this seal kit fits my sterndrive?
This kit is specifically for MerCruiser Alpha One Generation 2 sterndrives manufactured from 1991 onwards. It replaces OEM part 26-88397A1. Always verify your drive's model and year before ordering.
What are the signs of a failing upper unit seal?
Common signs include a milky or cloudy appearance in the gear lube (indicating water contamination), visible oil leaks around the upper housing, or a low gear lube level without obvious external leaks.
Can I install this kit myself?
While possible for experienced home mechanics with the correct tools, we strongly recommend professional installation. Correctly setting seal depth and ensuring proper alignment is critical to prevent leaks.
How often should these seals be replaced?
Seals should be inspected during regular annual service and replaced immediately if there are any signs of gear lube leakage or water intrusion. They are a common wear item that should not be overlooked.
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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