Upper Driveshaft Housing Seal Kit – Fits MerCruiser Alpha One Gen II (Replaces 26-88397A1, 88397A1)
Upper Driveshaft Housing Seal Kit – Fits MerCruiser Alpha One Gen II (Replaces 26-88397A1, 88397A1) 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
Upper Driveshaft Housing Seal Kit – Fits MerCruiser Alpha One Gen I...
Product Details
This Upper Driveshaft Housing Seal Kit is designed for MerCruiser Alpha One Gen II stern drives manufactured between 1991 and 2010 (serial numbers 0M400412 and up). It contains the essential seals and gaskets needed to service the upper driveshaft area, preventing water intrusion and gear lube leaks.
It serves as a direct replacement for Mercury/MerCruiser part numbers 26-88397A1 and 88397A1, and interchanges with Sierra 18-2644, GLM 87501, and Mallory 9-74302.
- Installs in the upper driveshaft housing of the stern drive.
- Engineered for use in marine environments.
- Includes all necessary seals and a gasket for a complete service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury/MerCruiser | 26-88397A1 |
| Mercury/MerCruiser | 88397A1 |
| Sierra | 18-2644 |
| GLM | 87501 |
| Mallory | 9-74302 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For MerCruiser models, it is crucial to check your engine's serial number to ensure correct fitment. This kit fits specific serial number ranges within the Alpha One Gen II series.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | Alpha One Gen II | All | 4-Stroke | 1991–1995 | 26-88397A1 | Serial Number D469859-F679999 |
| MerCruiser | Alpha One Gen II | All | 4-Stroke | 1996–1997 | 26-88397A1 | Serial Number F680000-K999999 |
| MerCruiser | Alpha One Gen II | All | 4-Stroke | 1998–2010 | 26-88397A1 | Serial Number L100040 & Up |
| MerCruiser | Alpha One Gen II (CR) | All | 4-Stroke | 1991–1995 | 26-88397A1 | Serial Number D469859-F679999 |
| MerCruiser | Alpha One Gen II (CR) | All | 4-Stroke | 1996–2010 | 26-88397A1 | Serial Number F680000 & Up |
Technical Specs
- Product Type
- Driveshaft Housing Seal Kit
- Installation
- Upper Driveshaft Housing
- Dimensions
- Length: 102 mm (4.00"), Width: 95 mm (3.75"), Height: 25 mm (1.00")
- Weight
- 0.059 kg (0.13 lbs)
- Warranty
- 1 year (JLM Marine); OEM warranty for genuine MerCruiser parts
- Other Technical Attributes
- Fits Alpha One Gen II stern drives from 1991 & newer
What’s in the Box
- 2 x Oil Seal (26-66302)
- 1 x Oil Seal (26-823894)
- 1 x Gasket (12-19183)
Installation Notes
- Disconnect the vessel's battery and completely drain the gear lube from the stern drive.
- Carefully separate the upper and lower units of the stern drive assembly.
- Remove the upper driveshaft housing assembly to access the old seals.
- Press out the old seals and remove the gasket, taking note of their orientation before removal.
- Thoroughly clean the seal bores and all gasket mating surfaces, ensuring they are free of debris.
- Using a suitable seal driver, press the new seals into place until they are correctly seated.
- Install the new gasket and carefully reassemble the housing components.
- Rejoin the upper and lower drive units, tightening all bolts to the manufacturer's specified torque.
- Refill the drive with fresh, high-quality marine gear lube.
- Before operating the boat, inspect the drive for any signs of leaks.
Troubleshooting & FAQ
How do I know if this seal kit fits my MerCruiser drive?
This kit is specifically designed for MerCruiser Alpha One Gen II stern drives from 1991 to 2010 (serial number 0M400412 & Up). To ensure a perfect match, please verify your drive's model and serial number against the ranges listed in the compatibility table.
What are the signs of a failed upper driveshaft seal?
Common symptoms include water in the gear lube (which gives it a milky or cloudy appearance), visible oil leaking from the upper housing area, or a recurring need to top off the gear lube level.
Can I replace just one seal from the kit?
While technically possible, it is strongly recommended to replace all seals and gaskets included in the kit at the same time. This comprehensive approach ensures a complete and lasting repair, preventing future leaks from other aged seals in the assembly.
How often should these seals be replaced?
There is no fixed replacement interval. Seals should be inspected for wear or damage during regular annual service and should be replaced whenever the drive unit is disassembled for other maintenance, or immediately if any signs of leakage are detected.
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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