816431A1;18-2747 U-Joint Rubber Bellow for Mercruiser Alpha One Gen 2 | JLM Marine

U-Joint Rubber Bellow for Mercruiser Alpha One Gen 2 – Transom Seal Kit 816431A1

This U-Joint Rubber Bellow is engineered for Mercruiser Alpha One Gen II Sterndrives, delivering reliable protection for the transom assembly. Designed to meet OEM specifications, this bellow ensures a secure seal and smooth operation in demanding marine environments.

This kit directly replaces Mercury Marine/Quicksilver OEM PN 816431A1, as well as aftermarket equivalents from Sierra Marine and GLM, offering broad compatibility and cost-effective maintenance for your sterndrive system.

• Complete kit includes U-Joint bellow, sleeve, and hose clamps for straightforward installation
• Direct replacement for Mercury Marine 816431A1, Sierra 18-2747, and GLM 89180
• Precision-fit design ensures compatibility with Alpha One Gen II sterndrive transom assemblies

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here's a guide to help you identify your engine's serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

This complete kit includes the following components:

• U-Joint Bellow
• Sleeve
• Hose Clamps

Installation Guide

1. Disconnect the battery and ensure the sterndrive is securely supported on a stable stand or hoist. Remove the drive unit from the transom assembly.
2. Carefully remove the old U-Joint bellow by loosening and sliding off the existing hose clamps. Inspect the U-Joint and gimbal bearing for wear or damage.
3. Clean the mounting surfaces on both the transom plate and the drive shaft housing thoroughly to remove old grease, debris, and corrosion.
4. Slide the new sleeve onto the drive shaft, ensuring proper alignment with the U-Joint assembly.
5. Position the new U-Joint bellow over the sleeve, aligning it carefully with the transom plate and drive shaft housing grooves.
6. Install the hose clamps at both ends of the bellow, tightening them evenly to the manufacturer's recommended torque specification. Ensure the bellow is seated properly without twists or kinks.
7. Apply marine-grade grease to the U-Joint and gimbal bearing as specified in your service manual.
8. Reinstall the sterndrive unit onto the transom, ensuring all mounting bolts are torqued to specification. Reconnect the shift and throttle cables.
9. Reconnect the battery and perform a visual inspection of the bellow installation, checking for proper seating and secure clamp tension.
10. Conduct a water test to verify proper operation and inspect for any signs of leakage around the bellow.

Troubleshooting & FAQ

Q: How do I confirm this bellow fits my Mercruiser sterndrive?
A: Verify that you have a Mercruiser Alpha One Gen II sterndrive and cross-reference your current part number with 816431A1, Sierra 18-2747, or GLM 89180. Always compare the bellow dimensions and profile with your original part before installation.

Q: How often should I replace the U-Joint bellow?
A: Inspect the U-Joint bellow annually as part of routine maintenance. Replace it every 2–3 years or immediately if you notice cracks, tears, swelling, or water intrusion, as a compromised bellow can lead to gimbal bearing and U-Joint failure.

Q: What are the signs that my U-Joint bellow has failed?
A: Common symptoms include water in the bilge, visible cracks or splits in the rubber, excessive play in the sterndrive, corrosion on the U-Joint or gimbal bearing, and difficulty steering. If you observe any of these, inspect and replace the bellow immediately.

Q: Can I install this bellow without removing the entire sterndrive?
A: While some experienced technicians may attempt partial removal, it is highly recommended to fully remove the sterndrive unit for proper access, cleaning, and inspection of the U-Joint and gimbal bearing. This ensures a thorough and safe installation.

Q: Is this an OEM or aftermarket part?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.