Exhaust Tube Bellows – Fits MerCruiser Alpha One & Bravo I/II/III Sterndrives (Replaces 78458A1)

Exhaust Tube Bellows – Fits MerCruiser Alpha One & Bravo I/II/III Sterndrives (Replaces 78458A1)

This marine exhaust tube bellows is designed to fit MerCruiser R/MR/Alpha One sterndrives (1983–1990, serial number 6225577 & UP), Bravo I, II, and III models (1988 and later, serial number OB664190 & UP), and Blackhawk sterndrives (1994-1995, serial number 0F18677 & UP).

It serves as a direct replacement for multiple OEM and aftermarket part numbers, ensuring precise fitment and reliable performance.

• Engineered for MerCruiser stern drive applications.
• Made from durable rubber to withstand the marine environment.
• Includes one bellows and the necessary stainless steel clamps for installation.

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 kit includes the following components:

• 1 x Exhaust Tube Bellows (Replaces 78458A1)
• 1 x Set of Stainless Steel Clamps

Installation Guide

Follow these general steps for installation. Professional installation is always recommended.

1. Safety First: Disconnect the boat’s battery and ensure the engine is off and cool.
2. Position the Drive: Trim the sterndrive to the full upward "trailer" position to access the bellows.
3. Remove Old Bellows: Loosen and remove the clamps securing the old exhaust bellows. You may need to carefully cut the old rubber bellows to remove it.
4. Clean Surfaces: Thoroughly clean the mounting grooves on the bell housing and gimbal housing. Ensure all old rubber, sealant, and debris are removed for a proper seal.
5. Install New Bellows: Fit the new exhaust bellows into position. Ensure it is properly seated in the grooves on both ends.
6. Secure Clamps: Install the new stainless steel clamps and tighten them securely. Do not overtighten, but ensure they are snug enough to prevent leaks.
7. Final Check: Lower the sterndrive, reconnect the battery, and start the engine. Check for any signs of exhaust or water leaks around the new bellows.

Troubleshooting & FAQ

How do I confirm this fits my MerCruiser sterndrive?
Verify your sterndrive model and serial number. This bellows fits MerCruiser R/MR/Alpha One (1983–1990, serial number 6225577 & UP), Bravo I/II/III (1988 and later, serial number OB664190 & UP), and Blackhawk (1994-1995, serial number 0F18677 & UP). It is a direct replacement for OEM part 78458A1.

What are the signs of a failed exhaust bellows?
Common indicators of a worn-out bellows include visible cracks or splits in the rubber, a noticeably louder exhaust sound, or water entering your boat’s bilge, especially when the drive is trimmed up.

How often should I replace the exhaust bellows?
As a key part of sterndrive maintenance, it's recommended to inspect all bellows annually. For preventative care, replacement is advised every 3-5 years, depending on usage (freshwater vs. saltwater) and storage conditions.

OEM vs. Aftermarket?
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.

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 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.