Driveshaft Housing Seal Kit – Fits Mercury/MerCruiser Alpha One Gen II (Replaces 26-88397A1, 88397A1)
Driveshaft Housing Seal Kit – Fits Mercury/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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Delivery and Shipping
Delivery and Shipping
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Driveshaft Housing Seal Kit – Fits Mercury/MerCruiser Alpha One Gen...
Product Details
This Driveshaft Housing Seal Kit is engineered for MerCruiser Alpha One Generation II stern drives manufactured from 1991 and newer. It contains the essential seals and gaskets to service the upper driveshaft housing, effectively preventing gear oil leaks and ensuring proper drivetrain lubrication.
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.
- Seals the upper driveshaft housing to prevent oil leaks.
- Fits all Alpha One Gen II models from 1991 to current.
- Includes all necessary seals and gaskets for the job.
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.
This kit is specific to Mercury/MerCruiser Alpha One Gen II models.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Mercury/MerCruiser | Alpha One Gen II | All | 4-Stroke | 1991 and newer | 26-88397A1 | Specifically for stern drives from serial number 0M400412 and up |
Technical Specs
- Product Type
- Driveshaft Housing Seal Kit
- Installation
- Upper Driveshaft Housing
- Dimensions
- Length: 102mm (4.00"), Width: 95mm (3.75"), Height: 25mm (1.00")
- Weight
- 0.059kg (0.13 lbs)
- Other Technical Attributes
- Fits Alpha One Gen II (Two) stern drives 1991 & newer
What’s in the Box
- 1 x Oil Seal (26-66302)
- 1 x Oil Seal (26-66302)
- 1 x Oil Seal (26-823894)
- 1 x Gasket (12-19183)
Installation Notes
- Drain the gear lube completely from the sterndrive unit.
- Carefully separate the upper and lower units of the sterndrive.
- Access the upper driveshaft housing where the main drive gear is located.
- Use a seal puller or flat-head screwdriver to carefully remove the old, worn seals.
- Thoroughly clean the housing and sealing surfaces to remove any old sealant, corrosion, or debris.
- Gently tap the new oil seals into place using a seal driver or a socket of matching diameter. Ensure they are seated evenly.
- Install the new gasket on the clean housing surface.
- Reassemble the upper and lower sterndrive units, torquing bolts to manufacturer specifications.
- Refill the sterndrive with the correct type and amount of high-performance gear lube.
- After running the engine, check the gear lube level and inspect the housing for any signs of leaks.
Troubleshooting & FAQ
What are the signs of a failing driveshaft housing seal?
Common symptoms include a persistent oil leak from the upper part of the sterndrive, a noticeable drop in the gear lube monitor bottle level, or a visible oil sheen on the water around the drive.
Will this kit fit my exact Alpha One Gen II model?
This kit is designed for all MerCruiser Alpha One Generation II sterndrives made from 1991 to the present, specifically those with serial numbers 0M400412 and up. Always verify your drive's model and serial number before ordering.
Can I install this kit myself?
While DIY installation is possible for those with mechanical experience, a seal puller and driver are recommended for proper removal and installation without damaging the components. We recommend professional installation for best results.
How often should these seals be replaced?
There is no fixed replacement interval. Seals should be inspected for leaks during routine annual maintenance and replaced whenever the sterndrive is separated for other service (e.g., water pump impeller) or immediately if a leak is detected.
What causes these seals to fail?
Seal failure is typically caused by age, heat cycles, and normal wear. It can be accelerated by damage from foreign debris, such as fishing line wrapping around the propeller shaft and working its way up into the housing.
The kit has two identical seals (26-66302). Is this correct?
Yes, the inclusion of two identical oil seals is correct for the intended application on the Alpha One Gen II driveshaft housing assembly, which requires a back-to-back seal configuration.
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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