Driveshaft Housing Upper Unit Seal Kit – Fits Mercruiser Alpha One Gen II (Replaces Mercruiser 26-88397A1, Sierra 18-2644)
Driveshaft Housing Upper Unit Seal Kit – Fits Mercruiser Alpha One Gen II (Replaces Mercruiser 26-88397A1, Sierra 18-2644) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Driveshaft Housing Upper Unit Seal Kit – Fits Mercruiser Alpha One ...
Product Details
This Driveshaft Housing Upper Unit Seal Kit is engineered for Mercruiser Alpha One Generation II stern drives manufactured from 1991 to the present. It includes all the necessary seals to service the upper driveshaft housing, ensuring a reliable, leak-free repair and restoration of your drive system's integrity.
This kit serves as a direct interchange for Mercruiser 26-88397A1, Sierra 18-2644, GLM 87501, and JRKZRAML 88397A1, providing a comprehensive solution for your maintenance needs.
- Engineered for direct-fit installation.
- Includes all required seals for a complete upper driveshaft housing service.
- Constructed from high-quality rubber and metal components to withstand the marine environment.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercruiser | 26-88397A1 |
| Sierra | 18-2644 |
| GLM | 87501 |
| JRKZRAML | 88397A1 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Years | OEM Part No. | Notes |
|---|---|---|---|---|
| Mercruiser | Alpha One Gen II | 1991–Present | 26-88397A1 | For upper driveshaft housing |
Technical Specs
- Product Type
- Upper Driveshaft Housing Seal Kit
- Installation
- Direct replacement
- Housing Material
- Various (Rubber, Metal)
- Weight
- 0.023 kg (0.8 oz)
- Fitment
- For Alpha One Gen II stern drives
- Warranty
- Varies by manufacturer
What’s in the Box
- 1 x Upper Driveshaft Housing Seal Kit (26-88397A1)
Installation Notes
- Ensure the engine is off and the battery is disconnected before starting work.
- Place the stern drive in the full tilt position for easier access.
- Drain the gear lube from the upper housing completely.
- Carefully remove the upper driveshaft housing cover and associated components, keeping track of their order.
- Extract all old seals and gaskets from the housing. Thoroughly clean all surfaces of old sealant, oil, and debris.
- Lightly lubricate the new seals with 2-4-C marine grease before installation.
- Use an appropriate seal driver to press the new seals into place evenly, avoiding damage.
- Reassemble the driveshaft housing components in the reverse order of disassembly.
- Refill the drive with the manufacturer-recommended high-performance gear lube to the correct level.
- After reassembly, check for any leaks before operating the vessel in the water.
Troubleshooting & FAQ
How do I confirm this kit fits my Mercruiser drive?
This kit is specifically for Mercruiser Alpha One Generation II drives from 1991 to present. The easiest way to confirm is by checking your drive's serial number or identifying it visually as a Gen II model. Cross-reference your existing seal kit part number with the numbers listed in our Part Number Matrix.
What are common signs of a failing upper driveshaft seal?
The most common symptom is water intrusion into the gear lube, which makes the oil appear milky or creamy. You may also notice gear oil leaking externally around the upper portion of the drive. A regular check of your gear lube reservoir can help detect this early.
How often should these seals be replaced?
There is no fixed replacement interval, but seals should be inspected annually as part of routine maintenance. It is recommended to replace them whenever the drive is disassembled for other service, or immediately if you detect any signs of water intrusion or oil leakage.
Is this aftermarket kit as good as the OEM version?
Yes, this kit is manufactured to meet or exceed OEM specifications. It uses comparable materials and is produced in an ISO 9002 certified facility to ensure quality, fit, and long-term durability in the marine environment, offering a reliable alternative to the original part.
Should I use the entire kit or just the one seal that failed?
For a complete and lasting repair, it is highly recommended to replace all seals and gaskets included in the kit. The other seals have been exposed to the same age and operating conditions and may be close to failing. Replacing the full set ensures the integrity of the entire housing.
What is the difference between an Alpha One Gen I and Gen II drive?
The Alpha One Gen II (1991+) has a different water pump and gear housing design. A quick visual cue is the trim ram configuration and the shape of the cavitation plate. The Gen II also has a single-piece gear lube monitor bottle hose, whereas the Gen I has a two-piece hose.
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.
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