Lower Unit Seal Kit – Fits Volvo Penta SX Sterndrives (Replaces 3850597)
Lower Unit Seal Kit – Fits Volvo Penta SX Sterndrives (Replaces 3850597) 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
Lower Unit Seal Kit – Fits Volvo Penta SX Sterndrives (Replaces 385...
Product Details
This aftermarket Lower Unit Seal Kit is designed for the lower gearcase unit on Volvo Penta SX sterndrives. It includes the various seals, O-rings, and gaskets necessary to prevent water intrusion and maintain proper lubrication in the lower drive unit, ensuring long-lasting performance.
It serves as a direct replacement for Volvo Penta 3850597, OMC 987251/778148, and Evinrude Johnson BRP 778148.
- Engineered for SX series drive applications.
- Includes essential components to service the lower gearcase.
- Professional installation is recommended for optimal results.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Volvo Penta | 3850597 | |
| OMC | 987251/778148 | |
| Evinrude Johnson BRP | 778148 | BRP equivalent part |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This kit is designed for the Volvo Penta SX, SX-C, SX-M, and SX-R lower gearcase units.
It also serves as a direct replacement for OMC Cobra applications using the specified part numbers.
| Brand | Model | OEM Part No. | Notes |
|---|---|---|---|
| Volvo Penta | SX | 3850597 | Lower gearcase seal kit |
| Volvo Penta | SX-C | 3850597 | Lower gearcase seal kit |
| Volvo Penta | SX-M | 3850597 | Lower gearcase seal kit |
| Volvo Penta | SX-R | 3850597 | Lower gearcase seal kit |
| OMC | Cobra | 987251 | Superseded by 778148 |
Technical Specs
- Product Type
- Lower Unit Seal Kit
- Housing Material
- Various (rubber, metal, composite)
- Product Dimensions
- 10.88" x 8.0" x 1.75"
- Weight
- 0.22 lbs (0.1 kg)
- Other Technical Attributes
- For SX series drive applications
- Warranty
- Manufacturer standard warranty
What’s in the Box
- Complete set of seals, O-rings, and gaskets for lower unit service (equivalent to 3850597)
Installation Notes
- Disconnect the battery and ensure the sterndrive is in the full down position.
- Drain the gearcase lubricant completely into an approved container.
- Carefully disassemble the lower unit according to the manufacturer's service manual.
- Remove all old seals, O-rings, and gaskets. Take care not to scratch or gouge any sealing surfaces.
- Thoroughly clean all components and sealing surfaces of old sealant and debris.
- Lightly lubricate the new seals and O-rings with marine grease before installation.
- Install the new components using appropriate seal drivers to ensure they are seated correctly.
- Reassemble the lower unit, torquing all fasteners to the manufacturer's specified values.
- Refill the gearcase with new, recommended lubricant to the proper level.
- After reassembly, check carefully for any signs of oil or water leaks before returning to service.
Troubleshooting & FAQ
How do I know if this seal kit fits my sterndrive?
This kit is specifically designed for Volvo Penta SX, SX-C, SX-M, and SX-R sterndrive lower units. It is also a direct cross-reference for OMC part 987251 and BRP/Evinrude Johnson part 778148. Always verify your engine model and original part number before ordering.
What are the signs of a failed lower unit seal?
The most common sign is a milky or cloudy appearance in your gear lube, which indicates water contamination. You may also notice gear oil leaking from the propeller shaft area or from the weep holes on the sterndrive.
Do I need special tools for installation?
Yes, installation typically requires specific tools such as a bearing carrier puller, seal drivers, and a torque wrench to ensure proper assembly and sealing. Due to the complexity and tool requirements, professional installation is highly recommended.
How often should lower unit seals be replaced?
Seals should be inspected for leaks every time you change your gear lube (at least annually). We recommend replacing them every 3-5 years as preventative maintenance, or immediately if you discover any signs of water intrusion or oil leakage.
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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