U-Joint Shift Bellows Kit – Fits OMC Cobra (1986 & Later) and Volvo Penta SX/DP Models (Replaces 3854270, 3858631)
U-Joint Shift Bellows Kit – Fits OMC Cobra (1986 & Later) and Volvo Penta SX/DP Models (Replaces 3854270, 3858631) is backordered and will ship as soon as it is back in stock.
Worry-free returns
Worry-free returns
Shop with confidence. If you’re not completely satisfied, eligible items may be returned within the return window, provided they are unused and in original packaging.
If the return is due to our error or a defective item, we’ll make it right.
Please contact us before returning any item.
Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
International delivery times may vary due to customs processing.
Tracking information will be provided once your order ships.
U-Joint Shift Bellows Kit – Fits OMC Cobra (1986 & Later) and V...
U-Joint Shift Bellows Kit – Fits OMC Cobra (1986 & Later) and Volvo Penta SX/DP Models (Replaces 3854270, 3858631) is backordered and will ship as soon as it is back in stock.
Product Details
This U-Joint Shift Bellows Kit is designed as a direct replacement for OMC Cobra sterndrive models (1986 and later, without cone clutch) and a wide range of Volvo Penta SX and DP series models. It protects the critical u-joint and drive components from water intrusion, ensuring longevity and reliable performance.
This kit provides a direct interchange for several OEM and aftermarket part numbers, including OMC and Volvo Penta 3854270/3858631, GLM 21962, Sierra 18-2771, and Mallory 9-72930.
- Engineered for direct replacement with OEM-matching fittings.
- Manufactured from durable rubber/neoprene to OEM specifications.
- Includes the necessary clamp for a secure installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| OMC Stern Drive | 3854270 |
| OMC Stern Drive | 3858631 |
| Volvo Penta | 3854270 |
| Volvo Penta | 3858631 |
| GLM | 21962 |
| Sierra | 18-2771 |
| Mallory | 9-72930 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For OMC Cobra models from 1986 and later, this bellow applies to sterndrives that do not use a cone clutch.
For Volvo Penta, this part fits various SX and DP outdrives. Verify your specific model against the list below.
| Brand | Model | Years | OEM Part No. | Notes |
|---|---|---|---|---|
| OMC | Cobra | 1986 & Later | 3854270/3858631 | Without cone clutch |
| Volvo Penta | SX-S | 3854270/3858631 | ||
| Volvo Penta | SX-C | 3854270/3858631 | ||
| Volvo Penta | SX-R | 3854270/3858631 | ||
| Volvo Penta | SX-M | 3854270/3858631 | ||
| Volvo Penta | DP-S | 3854270/3858631 | ||
| Volvo Penta | DP-S1 | 3854270/3858631 | ||
| Volvo Penta | DP-SM | 3854270/3858631 |
Technical Specs
- Product Type
- U-Joint Shift Bellows Kit
- Installation
- Direct replacement
- Connection
- OEM-matching fittings
- Housing Material
- Rubber/neoprene
- Housing Color
- Black
- Fitting Type
- OEM-compatible fittings with clamps
- Warranty
- 1 year manufacturer's warranty
- Other Technical Attributes
- Manufactured to OEM specifications using the exact same material as the originals. Produced in an ISO9002 certified factory.
What’s in the Box
- 1 x U-Joint Bellows with Clamp (Replaces 3854270/3858631)
Installation Notes
- Disconnect the boat's battery for safety.
- Tilt the sterndrive to the full "up" or "trailer" position to access the bellows.
- Carefully remove the old clamps and cut away the old bellow. Inspect the drive for any signs of water intrusion or damage.
- Thoroughly clean the mounting surfaces on both the transom assembly and the sterndrive.
- Fit the new bellows into position, ensuring it is properly seated on both ends.
- Securely fasten the new clamps. Do not overtighten, but ensure they are snug enough to create a watertight seal.
- Lower the sterndrive and inspect the bellow to ensure it collapses correctly and is not pinched.
- After launching the boat, check for any signs of leaks around the new installation before operating at speed.
Troubleshooting & FAQ
How do I confirm this bellow fits my specific boat?
The best way is to match your existing part number to one of the cross-reference numbers listed in our Part Number Matrix. If you can't find a part number, check your engine model and year against the Engine & Model Compatibility table. When in doubt, consult a marine mechanic.
What are common signs of a failing u-joint bellow?
Visible cracks, splitting, or perishing of the rubber are clear signs of failure. You may also find water inside the boat near the transom assembly or notice a milky, emulsified appearance in your sterndrive gear lube, which indicates water contamination due to a leak.
How often should this part be replaced?
U-joint bellows should be inspected annually for any signs of wear, cracking, or deterioration. A routine replacement interval of every 3-5 years is recommended for preventative maintenance, or immediately if any damage is found.
Is this the same as an exhaust bellow?
No, they are different parts with different functions. The u-joint bellow seals the driveshaft and protects the u-joints as they pass through the transom. The exhaust bellow provides a flexible connection for the engine's exhaust gases. Ensure you are ordering the correct part for your needs.
Can I reuse my old clamps?
It is strongly recommended to use the new clamps provided in the kit. Old clamps can lose their tension, corrode, or become fatigued, which may lead to an improper seal and subsequent water damage.
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.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
