Exhaust Tube Bellows – Fits MerCruiser Alpha One & Bravo Stern Drives (Replaces 78458A1)
Exhaust Tube Bellows – Fits MerCruiser Alpha One & Bravo Stern Drives (Replaces 78458A1) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Exhaust Tube Bellows – Fits MerCruiser Alpha One & Bravo Stern ...
Product Details
This Exhaust Tube Bellows is designed for a broad range of MerCruiser stern drives, including R, MR, Alpha One, Alpha One Gen II, and Bravo I/II/III models manufactured from 1963 to present, as well as Blackhawk models (1994–1995). It facilitates the dissipation of excess exhaust gas before it reaches the sterndrive.
This part is a direct replacement for MerCruiser 78458A1, Sierra 18-2760, CEF 500520K, GLM 89150, OMC/Johnson/Evinrude 0508711/0775482, and Mallory 9-72810.
- Engineered for high-performance applications and recommended for engines exceeding 300 HP.
- Attaches securely to the transom side bell housing for a reliable seal.
- The package includes the exhaust bellows, a stainless steel clamp, and a clip for a complete installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| MerCruiser | 78458A1 |
| Sierra | 18-2760 |
| CEF | 500520K |
| GLM | 89150 |
| OMC/Johnson/Evinrude | 0508711 |
| OMC/Johnson/Evinrude | 0775482 |
| Mallory | 9-72810 |
Engine & Model Compatibility
Confirm your engine model and year in the table below to ensure correct fitment.
| Brand | Model | Years | OEM Part No. | Notes |
|---|---|---|---|---|
| MerCruiser | R, MR | 1963–1990 | 78458A1 | Fits Serial No. 6225577 & UP (1983-1990) |
| MerCruiser | Alpha One | 1983–1990 | 78458A1 | Fits Serial No. 6225577 & UP |
| MerCruiser | Alpha One Gen II | 1991–Present | 78458A1 | |
| MerCruiser | Bravo I, II, III | 1988–Present | 78458A1 | Fits Serial No. OB664190 & UP |
| MerCruiser | Blackhawk | 1994–1995 | 78458A1 | Fits Serial No. 0F18677 & UP |
| OMC/Johnson/Evinrude | 0508711, 0775482 |
Technical Specs
- Product Type
- Exhaust Tube Bellows
- Installation
- Attaches to transom side only (bell housing)
- Connection
- Bell housing to outdrive
- Housing Material
- Stainless Steel & Rubber
- Housing Color
- Black
- Fitting Type
- Clamp-on
- Other Technical Attributes
- Recommended for engines with more than 300 HP; Allows excess exhaust gas to dissipate before the drive
What’s in the Box
- 1 x Exhaust Tube Bellows (78458A1)
- 1 x Stainless Steel Clamp
- 1 x Clip
Installation Notes
- Disconnect the negative battery terminal and ensure the engine is off and cool.
- Gain clear access to the exhaust bellows connecting the bell housing and the outdrive.
- Carefully remove the old clamps securing the existing bellows.
- Pry or cut the old bellows off the bell housing and drive, noting its orientation.
- Thoroughly clean the mounting surfaces on the bell housing and drive to remove any old sealant or debris.
- Position the new exhaust bellows onto the bell housing first.
- Secure the bellows to the bell housing using the new stainless steel clamp and clip provided.
- Double-check that the bellows is evenly seated and the clamp is tight.
- Reconnect the battery, start the engine, and check for any exhaust or water leaks around the new bellows.
Troubleshooting & FAQ
How do I know if this exhaust bellows will fit my engine?
This part fits a wide range of MerCruiser stern drives from 1963 to present, including R, MR, Alpha One/Gen II, and Bravo I/II/III models. Please check the "Engine & Model Compatibility" table and verify your serial number to ensure a perfect match.
What are the signs of a failing exhaust bellows?
Common symptoms include water leaking into the bilge, an unusually loud exhaust note from the stern, or visible cracks, splits, and deterioration on the rubber bellows itself. A failing bellows can lead to significant water damage, so it is critical to inspect it regularly and replace it as needed.
Is this bellows suitable for high-performance engines?
Yes, this exhaust tube bellows is specifically recommended for engines rated over 300 HP. It is designed to allow excess exhaust gas to dissipate before the drive, which is beneficial for higher-output applications.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials and manufactured in an ISO 9002 facility, where it is batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free, and expedited options will appear at checkout where available.
Warranty & returns?
This product is covered by a 1-year warranty against manufacturing defects under normal use. If any issues arise, contact our support team with your order details. Returns are accepted within our standard window for items that are unused and in their original condition. See our policy page or reach out for instructions.
Safety & Important Info
- Verify images and specifications against your original part before purchase. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement component, not an OEM part.
- Professional installation is recommended for safety and optimal performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or quality control.
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