Exhaust Tube Bellows – Fits MerCruiser R/MR/Alpha One & Bravo I/II/III (Replaces 78458A1, 18-2760)
Exhaust Tube Bellows – Fits MerCruiser R/MR/Alpha One & Bravo I/II/III (Replaces 78458A1, 18-2760) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
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Exhaust Tube Bellows – Fits MerCruiser R/MR/Alpha One & Bravo I...
Exhaust Tube Bellows – Fits MerCruiser R/MR/Alpha One & Bravo I/II/III (Replaces 78458A1, 18-2760) is backordered and will ship as soon as it is back in stock.
Product Details
This marine Exhaust Tube Bellows is designed for MerCruiser sterndrives, including R/MR/Alpha One models from 1983–1990 (serial number 6225577 & up), Bravo I, II, and III models from 1988 and later (serial number OB664190 & up), and Blackhawk models from 1994–1995 (serial number 0F18677 & up).
It serves as a direct replacement for multiple OEM and aftermarket part numbers, including Mercury 78458A1, Sierra 18-2760, GLM 89150, and Mallory 9-72810.
- Engineered for direct-fit, OEM-equivalent installation.
- Constructed from durable rubber to withstand the harsh marine environment.
- Includes essential stainless steel clamps for a complete and secure installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 78458A1 |
| Sierra | 18-2760 |
| GLM | 89150 |
| Mallory | 9-72810 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For MerCruiser applications, verify that your sterndrive model and serial number range match the compatibility data listed.
| Brand | Model | Years | OEM Part No. | Notes |
|---|---|---|---|---|
| MerCruiser | R/MR/Alpha One | 1983–1990 | 78458A1 | Serial No. 6225577 & UP |
| MerCruiser | Bravo I, II, III | 1988+ | 78458A1 | Serial No. OB664190 & UP |
| MerCruiser | Blackhawk | 1994–1995 | 78458A1 | Serial No. 0F18677 & UP |
Technical Specs
- Product Type
- Exhaust Tube Bellows
- Fitment
- OEM Replacement
- Installation
- Direct Replacement
- Housing Material
- Rubber
- Application
- MerCruiser Stern Drives
- Package Contents
- Bellows with stainless steel clamps
- OEM Reference
- 78458A1, 18-2760, 9-72810, 89150
What’s in the Box
- 1 x Exhaust Tube Bellows (Replaces 78458A1)
- 1 x Set of Stainless Steel Clamps
Installation Notes
- Ensure the engine is off, cool to the touch, and the battery is disconnected for safety.
- Trim the sterndrive to the full "up" or "trailer" position to access the bellows.
- Locate and loosen the clamps on both ends of the old exhaust bellows, then carefully pry it off the bell housing and exhaust tube.
- Thoroughly clean the mounting grooves on both surfaces, removing any old sealant or debris.
- Fit the new exhaust bellows into position, ensuring it is properly seated in the grooves on both ends.
- Securely fasten the new stainless steel clamps. Tighten them to the manufacturer's recommended torque specification to prevent leaks.
- Lower the sterndrive, reconnect the battery, and start the engine in the water, checking carefully for any signs of exhaust leaks around the new bellows.
Troubleshooting & FAQ
How do I know if this bellows will fit my engine?
This bellows fits specific MerCruiser sterndrives: R/MR/Alpha One (1983–1990), Bravo I/II/III (1988+), and Blackhawk (1994–1995). Always verify your model and, most importantly, the serial number range provided in the compatibility list before ordering.
What are the signs of a failing exhaust bellows?
Common signs include visible cracks, splits, or perishing rubber. You may also notice an unusually loud exhaust noise or water entering the bilge area, both of which can indicate a leak that requires immediate attention.
How often should the exhaust bellows be replaced?
As a critical preventative maintenance item, it is recommended to inspect bellows annually for wear and tear. Replacement is typically advised every 3-5 years, depending on hours of use and exposure to saltwater versus freshwater.
Is this part different from the original Mercury part?
This is an aftermarket part designed to meet or exceed OEM specifications for fit, form, and function. It offers a cost-effective alternative to the original 78458A1 part while ensuring reliable performance and durability.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and 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 QC.
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