U-Joint Bellows – Fits MerCruiser Alpha One Gen II & Vazer Sterndrives (Replaces 816431A1)
U-Joint Bellows – Fits MerCruiser Alpha One Gen II & Vazer Sterndrives (Replaces 816431A1) is backordered and will ship as soon as it is back in stock.
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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
U-Joint Bellows – Fits MerCruiser Alpha One Gen II & Vazer Ster...
Product Details
This U-Joint Bellows – Fits MerCruiser Alpha One Gen II & Vazer Sterndrives (Replaces 816431A1) assembly is designed for MerCruiser Alpha One Gen II and Vazer sterndrives from 1991 and newer models. It serves as a crucial component to prevent water from entering the bell housing and damaging the u-joint and gimbal bearing.
It is a direct aftermarket replacement for Mercury/Quicksilver 816431A1 and interchanges with Sierra 18-2747, GLM 89180, and Mallory 9-72704.
- Direct OEM replacement fit for straightforward installation.
- Constructed from durable, flexible composite rubber for longevity.
- Includes essential installation hardware such as clamps and a grounding clip.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number |
|---|---|
| Mercury/Quicksilver | 816431A1 |
| Sierra | 18-2747 |
| GLM | 89180 |
| Mallory | 9-72704 |
| CEF | 500515K |
| AM | AM816431A1 |
| REC | REC816431A1 |
Engine & Model Compatibility
Confirm your engine model and year in the table below to ensure accurate fitment.
For MerCruiser Sterndrives: This part fits Alpha One Gen II models manufactured from 1991 to present, as well as all Vazer sterndrive models.
| Brand | Model | Years | OEM Part No. | Notes |
|---|---|---|---|---|
| MerCruiser | Alpha One Gen II | 1991–1995 | 816431A1 | |
| MerCruiser | Alpha One Gen II | 1996–1997 | 816431A1 | |
| MerCruiser | Alpha One Gen II | 1998 and up | 816431A1 | |
| MerCruiser | Vazer | All years | 816431A1 |
Technical Specs
- Product Type
- U-Joint Bellows Assembly
- Installation
- Direct OEM replacement
- Housing Material
- Flexible composite rubber
- Function
- Prevents water intrusion through bell housing
- Includes Hardware
- Yes, hose clamps for both ends
- Installation Difficulty
- Medium, requires common tools
- Weight
- 0.51 kg (1.13 lb)
What’s in the Box
- 1 x U-Joint Bellows (Replaces 816431A1)
- 1 x Grounding Clip (54-86049)
- 1 x Worm Gear Clamp (54-815504372)
- 1 x Sleeve (816607)
Installation Notes
- Safely secure the vessel and place the sterndrive in the fully trimmed down position.
- Remove the sterndrive assembly from the bell housing according to the manufacturer's service manual.
- Carefully remove the old bellows and clamps. Thoroughly clean the mounting surfaces on the bell housing and gimbal housing.
- Install the new bellows, ensuring the grounding clip makes proper contact if applicable.
- Secure both ends of the new bellows with the provided hose clamps, tightening them to the specified torque. Confirm a secure, watertight seal.
- Reinstall the sterndrive assembly, ensuring correct alignment of the u-joint shaft.
- After reassembly, lower the drive and check carefully for leaks in a controlled environment before full operation on the water.
Troubleshooting & FAQ
How do I know if my u-joint bellows needs replacement?
Common signs of failure include visible cracks, tears, or brittleness in the rubber. Water found inside the bellows or a rusty u-joint/gimbal bearing are definitive indicators that a replacement is overdue.
What is the recommended maintenance interval for this part?
U-joint bellows should be inspected annually for signs of wear or damage. As a preventative measure, it's wise to replace them every 3-5 years, or immediately if any damage is discovered.
Will this fit sterndrive models other than Alpha One Gen II?
This bellows is specifically designed for MerCruiser Alpha One Gen II (1991+) and Vazer sterndrives. It will not fit Alpha One Gen I, Bravo, or other models. Always verify your drive model before ordering.
What happens if a u-joint bellows fails during operation?
A failed bellows allows water to flood the bell housing, which will quickly destroy the gimbal bearing and u-joints. This can lead to catastrophic drive system failure, loss of propulsion, and costly repairs.
Do I need special tools for installation?
Installation requires removing the sterndrive, which involves standard mechanic's tools, a socket set, and torque wrench. A bellows expansion tool can make the process easier. Bellows adhesive is also recommended for a secure seal.
Is there a difference between this and the OEM part?
This aftermarket part is engineered to meet or exceed OEM specifications for fit, material quality, and performance. It provides a reliable and cost-effective alternative to OEM components.
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 and specifications against 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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