Lower Unit Gearcase Seal Kit – Fits Volvo Penta SX & OMC Cobra SX 3.0-8.2L V6/V8 (Replaces 3855275)
Lower Unit Gearcase Seal Kit – Fits Volvo Penta SX & OMC Cobra SX 3.0-8.2L V6/V8 (Replaces 3855275) is backordered and will ship as soon as it is back in stock.
Couldn't load pickup availability
Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Lower Unit Gearcase Seal Kit – Fits Volvo Penta SX & OMC Cobra ...
Product Details
This is a complete Lower Unit Gearcase Seal Kit designed for Volvo Penta SX and OMC Cobra SX sterndrives manufactured between 1994 and 2006. It fits a wide range of V4, V6, and V8 engines from 3.0L to 8.2L, providing a reliable solution for preventing water intrusion and oil leaks in the lower gearcase.
This kit serves as a direct aftermarket replacement for Volvo Penta 3855275, OMC 3855275, Sierra 18-2598, GLM 87750, and EMP 26-08532.
- Engineered for SX single propeller outdrives.
- Professional installation is highly recommended to ensure a proper seal.
- Kit components are made in the USA according to our supplier data.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| Volvo Penta | 3855275 |
| OMC | 3855275 |
| Sierra | 18-2598 |
| GLM | 87750 |
| EMP | 26-08532 |
Engine & Model Compatibility
Confirm your engine model and year in the tables below to ensure correct fitment.
Volvo Penta Applications: This kit is designed for SX single-propeller sterndrives from 1994 through 2006.
OMC Applications: This kit fits Cobra SX single-propeller sterndrives from 1994 through 1998 across various engine sizes.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Volvo Penta | SX Sterndrive | All HP Ratings | 4-Stroke | 1994–2006 | 3855275 | For SX single propeller outdrives |
| OMC | Cobra SX | 3.0L Models | 4-Stroke | 1994–1998 | 3855275 | For SX single propeller outdrives |
| OMC | Cobra SX | 4.3L V6 | 4-Stroke | 1994–1998 | 3855275 | For SX single propeller outdrives |
| OMC | Cobra SX | 5.0L–8.2L V8 | 4-Stroke | 1994–1998 | 3855275 | For SX single propeller outdrives |
Technical Specs
- Product Type
- Lower Unit (Gearcase) Seal Kit
- Installation
- Professional installation recommended
- Other Technical Attributes
- Made in USA (per JLM Marine source)
What’s in the Box
- 1 x Lower Gear Case Seal Kit (3855275)
- 1 x O-Ring (18-7145-9)
- 1 x O-Ring (18-7160-9)
- 1 x Water Supply Tube Seal (18-32882/3852315)
- 1 x Water Seal Tube (3854595)
- 2 x O-Rings (3852866/3852959)
Installation Notes
- Disconnect the negative battery cable for safety.
- Position a drain pan under the gearcase and remove the drain/fill plugs to empty the lubricant.
- Remove the propeller assembly.
- Unbolt and carefully lower the gearcase from the upper driveshaft housing.
- Disassemble the lower unit as required to access and remove the old seals, O-rings, and gaskets.
- Thoroughly clean all mating surfaces, removing any old sealant, corrosion, or residue.
- Carefully install the new seals and O-rings from the kit, ensuring they are properly seated and lubricated.
- Reassemble the gearcase components, torquing fasteners to manufacturer specifications.
- Mount the gearcase back onto the upper housing, ensuring the driveshaft and shift shaft align.
- Refill the gearcase with fresh, appropriate-grade marine gear lubricant until it flows from the upper vent hole.
- Reinstall the propeller and reconnect the battery cable.
- Check for leaks before operating the vessel in water.
Troubleshooting & FAQ
How do I know if my gearcase seals are failing?
The most common sign is milky, water-contaminated gear lube when you drain it. Other indicators include visible oil leaks around the propeller shaft or gearcase seams, or a frequent need to add lubricant.
Is this kit for a single or dual propeller outdrive?
This seal kit is designed specifically for SX single-propeller sterndrives from Volvo Penta and OMC. It is not compatible with DuoProp (DP) or other dual-propeller models.
What is the recommended replacement interval for these seals?
Seals should be inspected for leaks annually when changing the gear lube. As a preventative measure, it's good practice to replace them every 3-5 years or anytime the lower unit is serviced for other repairs.
What are the main causes of premature seal failure?
The most frequent causes are damage from fishing line wrapped around the propeller shaft, impact damage to the skeg or gearcase, incorrect installation, or simple age and wear.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials. Our parts are manufactured in an ISO 9002 facility and are batch-inspected for quality and consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free; expedited options will appear at checkout where available for your location.
Warranty & returns?
This product is covered by a 1-year warranty against manufacturing defects under normal use. If any issues arise, contact our support team with your order details. Returns are accepted within our standard window, provided the item is unused and in its original condition. See our policy page or reach out for instructions.
Safety & Important Info
- Verify images and specifications against your original part before purchase. If anything differs—even if your model appears on a compatibility list—do not order.
- This is an aftermarket replacement part, not an Original Equipment Manufacturer (OEM) component.
- Professional installation is strongly recommended for safety, performance, and to prevent premature part failure.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world conditions.
- Fast Global Fulfillment — We offer free standard delivery to most regions, with an average transit time of 5–15 days.
- Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without compromising on materials or quality control.
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.
