Lower Gear Case Seal Kit – Fits Volvo Penta SX & OMC Cobra Sterndrives (Replaces 3855275, 0778351)

Lower Gear Case Seal Kit – Fits Volvo Penta SX & OMC Cobra Sterndrives (Replaces 3855275, 0778351)

This lower gear case seal kit is designed for Volvo Penta SX series sterndrives (1994–2006) and OMC Cobra SX series sterndrives (1994–1998). It provides a comprehensive solution for repairing leaks and maintaining the integrity of single-propeller outdrives, fitting a wide range of engine models from 3.0L to 8.2L.

This kit serves as a direct replacement for Volvo Penta part numbers 3855275 and 0778351, as well as Sierra 18-2598 and GLM 87750, ensuring compatibility and reliable performance.

• Installation Type: Direct replacement for single propeller outdrives.
• Package Contents: Includes a complete 7-piece set of seals and O-rings.
• Fuel Compatibility: Designed for gasoline sterndrive engines.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below.

Technical Specifications

Package Contents

This 7-piece kit includes all necessary seals and O-rings for a lower gear case service:

• 1 x Seal Water Supply Tube (3854595)
• 1 x Seal Water Supply Tube (3852315)
• 1 x O-Ring Oil Passage (3852595)
• 1 x O-Ring Support Housing (3852866)
• 1 x O-Ring (3852865)
• 1 x O-Ring (333572)
• 1 x Oil Seal (3858303/3863090)

Installation Guide

Follow these general steps to replace the lower gear case seals:

1. Begin by draining all the gear lube from the sterndrive's lower unit.
2. Remove the propeller assembly, followed by the entire lower unit from the sterndrive.
3. Carefully disassemble the lower gear case to access the old seals. Pay close attention to the order and orientation of all components.
4. Remove the old seals, O-rings, and any gaskets. Take care not to scratch or damage the metal housing surfaces.
5. Thoroughly clean all sealing surfaces to remove old sealant, corrosion, or debris.
6. Lightly lubricate the new seals and O-rings with marine grease before installation.
7. Using a correctly sized seal driver tool, press the new seals into place until they are properly seated. Ensure they are not installed at an angle.
8. Reassemble the gear case components in the reverse order of disassembly.
9. Reinstall the lower unit onto the sterndrive, followed by the propeller.
10. Refill the lower unit with the manufacturer-specified fresh gear lube to the correct level.
11. After refilling, check carefully for any signs of leaks around the seals before operating the boat in the water.

Troubleshooting & FAQ

Q: How do I know if this seal kit will fit my sterndrive?
A: This kit is specifically designed for Volvo Penta SX series (1994–2006) and OMC Cobra SX series (1994–1998) sterndrives equipped with single propellers. To ensure a perfect match, please cross-reference your engine model and year with the detailed compatibility tables on this page.

Q: What are the common signs that my gear case seals are failing?
A: The most common indicators of a failing seal are milky, water-contaminated gear lube (which looks like a coffee milkshake), visible oil leaking from the lower unit (especially around the prop shaft), or a recurring need to add more gear lube. Any of these signs suggest it's time for an inspection and seal replacement.

Q: How often should I replace my lower unit seals?
A: It is best practice to inspect your gear lube at least once a year for any signs of water intrusion. We recommend replacing the seals as a preventative measure whenever the lower unit is being serviced or immediately if you detect a leak or fluid contamination.

Q: OEM vs. Aftermarket?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.