Lower Unit O-Ring Seal Kit – Fits Volvo Penta SX/DPS Series (Replaces 3852045, 3855081)

Lower Unit O-Ring Seal Kit – Fits Volvo Penta SX/DPS Series (Replaces 3852045, 3855081)

This lower unit o-ring seal kit provides essential seals for the dipstick, vent, and drain plugs on Volvo Penta SX, DPS, and related sterndrive series. The kit is engineered to prevent gear oil leakage and water intrusion, protecting your sterndrive's lower unit from premature wear and damage.

It serves as a direct replacement for multiple OEM and aftermarket part numbers, including Volvo Penta 3852045, 3855081; Sierra 18-7116, 18-7145; OMC 3852045; Mercury 25-20633; and Johnson/Evinrude 303067, among others.

• Installation Method: Direct fit replacement for existing plug o-rings.
• Function: Seals the gearcase dipstick, vent, and drain screw openings.
• Included: Contains three essential o-rings for a complete lower unit service.

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. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

For Johnson/Evinrude owners, here’s a guide to help you identify your engine’s serial/model: Johnson Serial Number Guide.

Volvo Penta Models

Mercury/OMC/Johnson/Evinrude Models

Technical Specifications

Package Contents

• 1 x Dipstick O-Ring (Replaces OEM Part Number 3852045)
• 1 x Vent O-Ring (Replaces OEM Part Number 3855081)
• 1 x Drain O-Ring (Replaces OEM Part Number 3855081)

Installation Guide

1. Ensure the engine is off and the sterndrive is trimmed down to a level position.
2. Place a suitable oil drain pan underneath the lower unit's drain screw.
3. Slowly remove the upper vent plug/dipstick and the lower drain screw to allow the gear oil to empty completely.
4. Carefully remove and discard the old o-rings from the dipstick and screws.
5. Clean the threads and sealing surfaces of the plugs and the gearcase housing.
6. Lightly coat the new o-rings with fresh gear lube and install them onto the dipstick and screws.
7. Reinstall the lower drain screw and fill the gearcase through the upper vent hole until oil begins to flow out.
8. Install the upper vent plug/dipstick and tighten both plugs to the manufacturer's specified torque. Do not overtighten.

Troubleshooting & FAQ

Q: How do I know if this o-ring kit fits my sterndrive?

A: This kit is designed for a wide range of Volvo Penta SX and DPS series sterndrives, along with select models from Mercury, OMC, and Johnson/Evinrude. To confirm fitment, please review the Compatible Engine Models table on this page and match your engine's model. Cross-referencing the OEM part numbers (e.g., Volvo Penta 3852045, 3855081) is the most reliable method.

Q: What are the signs that my lower unit o-rings need replacement?

A: The most common indicators are visible gear oil leakage around the drain, vent, or dipstick plugs, or milky/creamy-looking gear lube when you drain it. Milky oil signifies water intrusion, which is often caused by a failed o-ring seal.

Q: How often should I replace these o-rings?

A: It is standard maintenance practice to replace the drain and vent screw o-rings every time you change your lower unit's gear oil. This is typically recommended once per season or every 100 hours of engine operation, whichever comes first.

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.