Exhaust Tube Bellows – Fits MerCruiser Alpha One & Bravo Stern Drives (Replaces 78458A1)

Exhaust Tube Bellows – Fits MerCruiser Alpha One & Bravo Stern Drives (Replaces 78458A1)

This exhaust tube bellows is designed for MerCruiser stern drive models including R, MR, Alpha One, Alpha One Gen II, Bravo I/II/III (1963 and newer), and Blackhawk (1994–1995). It provides a reliable seal for the exhaust system between the bell housing and the outdrive.

This component is a direct replacement for MerCruiser 78458A1, Sierra 18-2760, CEF500520K, GLM 89150, OMC/Johnson/Evinrude 0508711/0775482, and Mallory 9-72810.

• Installation is on the transom side only (bell housing).
• Engineered to allow excess exhaust gas to dissipate before the drive, making it recommended for engines with more than 300 HP.
• Comes as a complete kit with a stainless steel clamp and clip for a secure fit.

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.

Confirm your engine model/year in the table below. For Johnson/Evinrude owners, here’s a guide to help you identify your engine’s serial/model: Johnson/Evinrude Serial Number Guide.

Technical Specifications

Package Contents

• 1 x Exhaust Tube Bellows (78458A1)
• 1 x Stainless Steel Clamp
• 1 x Clip

Installation Guide

1. Ensure the engine is off and the vessel is secure. Turn the sterndrive to one side for better access to the bellows.
2. Carefully remove the old exhaust tube bellows by loosening its clamps on the bell housing and outdrive.
3. Thoroughly clean the mounting surfaces on the bell housing and outdrive, removing any old adhesive, sealant, or debris.
4. Align the new exhaust tube bellows. It attaches to the transom side (bell housing) only.
5. Secure the bellows onto the bell housing using the new stainless steel clamp and clip provided.
6. Tighten the clamp securely, but avoid over-tightening to prevent damage to the rubber.
7. Once installed, check for a tight seal before operating the vessel in the water.

Troubleshooting & FAQ

Q: How do I confirm this exhaust bellows will fit my MerCruiser drive?

A: This part fits MerCruiser R, MR, Alpha One (Gen I & II), and Bravo (I, II, III) sterndrives from 1963 and newer. Please check the "Compatible Engine Models" table and verify your serial number to ensure an exact match. It replaces OEM part number 78458A1.

Q: What is the purpose of this exhaust bellows?

A: The exhaust tube bellows connects the bell housing to the outdrive, allowing excess exhaust gases to dissipate before reaching the drive. It is particularly recommended for engines with over 300 HP to manage exhaust flow effectively.

Q: What are the signs that my exhaust bellows needs replacement?

A: Common signs of a failing bellows include visible cracks or tears, a noticeable exhaust smell around the engine compartment, or water leaking into the bilge area through the transom assembly. A regular inspection is recommended.

Q: OEM vs. Aftermarket?

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.