78458A1 Exhaust Tube Bellow with Clamp – Fits MerCruiser R, MR, Alpha One, Alpha One Gen II, Bravo I/II/III & Blackhawk

Product Details

The 78458A1 Exhaust Tube Bellow is a replacement bell-housing exhaust tube for MerCruiser R, MR, Alpha One, Alpha One Gen II, Bravo I, Bravo II, Bravo III, and Blackhawk sterndrive applications. It connects the exhaust system components while allowing the flexibility required for engine and sterndrive movement.

This is a single exhaust tube bellow supplied with the included clamp. It replaces the MerCruiser 78458A1 reference and is listed for compatible MerCruiser stern-drive applications. Always compare the original component and connection points before installation.

• Replacement exhaust tube bellow for MerCruiser sterndrives
• Includes one clamp for installation
• Designed for R, MR, Alpha One, Alpha One Gen II, Bravo I/II/III, and Blackhawk applications
• Aftermarket replacement for the listed OEM reference

Part Number Matrix

Use this matrix to compare the manufacturer and aftermarket reference numbers listed for this exhaust tube bellow.

Engine & Model Compatibility

This exhaust tube bellow is listed for the following MerCruiser sterndrive families. Verify the exact drive configuration and compare the original part before ordering.

Technical Specs

Part Type

Exhaust tube bellow

OEM Reference

78458A1

Application

MerCruiser stern-drive bell-housing exhaust system

Included Clamp

1 clamp

Product Configuration

Single exhaust tube bellow with included clamp

What's in the Box

• 1 × Exhaust Tube Bellow
• 1 × Clamp

Installation Notes

1. Disconnect the battery and allow the engine and exhaust components to cool before beginning work.
2. Remove the damaged exhaust tube bellow by loosening and removing the existing clamp.
3. Inspect the mating surfaces and connected exhaust components for corrosion, cracks, debris, or other damage. Clean the surfaces thoroughly.
4. Position the replacement bellow over the correct exhaust tube connections and ensure that it is fully seated.
5. Position the included clamp over the bellow connection and tighten it securely according to the applicable service instructions. Do not overtighten.
6. Check that the bellow is properly aligned and that there are no gaps, folds, or partially seated edges.
7. Reconnect the battery and run the engine only after confirming that all components are secure.
8. Inspect the installation for exhaust leakage or unusual exhaust noise before returning the boat to service.

Troubleshooting & FAQ

How do I know if my exhaust tube bellow needs replacement?

Inspect the bellow for cracks, tears, hardening, splitting, or other visible deterioration. Exhaust leakage, unusual exhaust noise, or exhaust odor in the bilge can also indicate a failed or incorrectly seated bellow.

Will this fit my MerCruiser Alpha One Gen II?

This product is listed for MerCruiser Alpha One Gen II applications. Confirm the exact drive configuration and compare the original exhaust tube bellow and connection points before ordering.

Is this a complete kit?

This is a single exhaust tube bellow supplied with one included clamp. It is not a complete transom service kit or a complete sterndrive installation kit.

Can I reuse the old clamp?

Replacement of the clamp is recommended when installing the new bellow. This product includes one clamp; inspect the included clamp and the mating components before installation.

What tools are required for installation?

Typical installation requires basic hand tools suitable for removing and tightening the applicable clamp, along with any additional tools required to access the exhaust assembly on your specific sterndrive.

How often should the exhaust tube bellow be inspected?

Inspect the bellow during routine seasonal maintenance and whenever the sterndrive or exhaust system is serviced. Replace it if cracks, splits, hardening, deformation, or leakage is found.

Is this an OEM component?

No. This listing is for an aftermarket replacement exhaust tube bellow. The listed OEM reference is provided for identification and compatibility comparison.

Safety & Important Info

• Verify the drive model, original part, connection points, and included components before ordering.
• Do not operate the engine if the bellow is improperly seated or if an exhaust leak is present.
• Follow the applicable MerCruiser service procedures and use professional installation if you are unsure of the repair.
• Part-number references identify compatible comparison numbers and do not indicate that this product is manufactured by those brands.

About Sea Sierra

• Marine Replacement Parts — We supply replacement components for common marine engine and sterndrive service applications.
• Application-Focused Listings — Product information is organized around part type, reference numbers, and model compatibility.
• Practical Service Support — Compare the original component and verify the installation details before beginning repairs.