Aftermarket Exhaust Bellow Kit for Mercury MerCruiser Alpha One Gen II - Replaces 18654A1 816431A1 74639A2

Aftermarket Exhaust Bellow Kit for Mercury MerCruiser Alpha One Gen II

This comprehensiveexhaust bellow kit is designed for Mercury MerCruiser Alpha One Generation II stern drive systems. It provides a complete replacement solution for the three critical bellows components, protecting the marine engine from water intrusion. This kit is a direct replacement for OEM parts 18654A1, 816431A1, and 74639A2.

The kit includes an exhaust bellows, a U-joint bellows, and a shift cable bellows. Each component is manufactured from a flexible, ribbed composite engineered to withstand harsh marine environments, including saltwater exposure and temperature fluctuations. The advanced materials offer enhanced durability and longevity compared to original factory components. Each part meets or exceeds original equipment manufacturer (OEM) specifications.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM andbrands.

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.

Mercury MerCruiser Alpha One Generation II Models

Additional Compatible Models

Technical Specifications

Exhaust Bellows (Replaces 18654A1/8M0124227)

U-Joint Bellows (Replaces 816431A1)

Shift Cable Bellows (Replaces 74639A2)

Package Specifications

Package Contents

• 1 x Exhaust Bellows Assembly (Replaces 18654A1/8M0124227)
  • 2 x Stainless Steel Worm Gear Clamps
  • 2 x Grounding Clips
• 1 x U-Joint Bellows Assembly (Replaces 816431A1)
  • 1 x Stainless Steel Worm Gear Clamp
  • 1 x Grounding Clip
  • 1 x Bellows Sleeve (816607)
• 1 x Shift Cable Bellows Assembly (Replaces 74639A2)
  • Stainless Steel Clamps

Installation Guide

Installation requires intermediate mechanical skills and specialized tools. Professional installation is recommended. Proper installation is critical for preventing water intrusion and ensuring long-term reliability.

Required Tools and Skill Level:

• Skill level: Intermediate to Advanced
• Estimated installation time: 4-6 hours
• Exhaust bellows installation tool (recommended)
• Standard hand tools (wrenches, screwdrivers)
• Marine-grade bellows adhesive

Installation Summary:

1. Remove the stern drive unit to access the bellows.
2. Carefully remove the old bellows from their mounting points.
3. Thoroughly clean and inspect all mounting surfaces for damage.
4. Apply marine-grade adhesive to the mounting surfaces.
5. Install the new bellows, ensuring correct alignment. A specialized tool is recommended for seating the exhaust bellows.
6. Secure each bellows with the supplied clamps, tightening to the manufacturer's torque specifications.
7. Reinstall the stern drive unit and check for leaks.

Maintenance: Inspect bellows annually or every 100 hours of operation. Look for signs of wear such as cracking, hardening, or loss of flexibility. Replacement is recommended every 3-5 years depending on usage and conditions.

Troubleshooting & FAQ

How do I ensure this kit fits my MerCruiser engine?
To ensure fitment, you must verify your engine's serial number and model year. The primary compatibility is for MerCruiser Alpha One Gen II (1991-Current). Please check the detailed compatibility tables above and use the linked serial number guides to confirm your specific model before ordering.

What are the signs that my bellows need replacement?
Common signs of wear include visible cracks, hardening of the composite material, or loss of flexibility. During your annual inspection (or every 100 hours), squeeze the bellows to check for pliability. Any water found inside the boat's bilge area could also indicate a bellows failure.

What is the most common installation mistake?
The most frequent issues are improper alignment of the bellows and inadequate sealing. Not using sufficient marine-grade adhesive or failing to tighten the clamps to the correct torque can lead to leaks. Using a specialized installation tool for the exhaust bellows is highly recommended to ensure it seats correctly.

OEM vs. Aftermarket?
This listing is anreplacement 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.

How fast do you ship and how much does it cost?
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.

What is your warranty and return policy?
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 anreplacement 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.