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) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
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Lower Unit O-Ring Seal Kit – Fits Volvo Penta SX/DPS Series (Replac...
Lower Unit O-Ring Seal Kit – Fits Volvo Penta SX/DPS Series (Replaces 3852045, 3855081) is backordered and will ship as soon as it is back in stock.
Product Details
This Lower Unit O-Ring Seal Kit – Fits Volvo Penta SX/DPS Series (Replaces 3852045, 3855081) is designed for Volvo Penta SX, DPS, and related sterndrive series. It provides essential seals for the dipstick, vent, and drain plugs to prevent gear oil leakage and water intrusion in the lower unit.
This kit is a direct replacement for a wide range of part numbers, including Volvo Penta 3852045 and 3855081, Sierra 18-7116 and 18-7145, and various Mercury and Johnson/Evinrude equivalents.
- Engineered for a direct fit, simplifying installation.
- Made from durable rubber to ensure a reliable seal.
- Includes the three essential o-rings for a complete service.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Volvo Penta | 3852045 |
| Volvo Penta | 3855081 |
| Sierra | 18-7116 |
| Sierra | 18-7145 |
| GLM | 81100 |
| Johnson/Evinrude | 303067 |
| Johnson/Evinrude | 329381 |
| Johnson/Evinrude | 332584 |
| Mercury | 25-20633 |
| Mercury | 25-22174 |
| Mercury | 25-62704 |
| Mercury | 25-85148 |
| Mercury | 802206 |
| OMC | 303067 |
| OMC | 3852045 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Volvo Penta models, this kit fits various SX, DPS, DPX, and XDP series drives.
| Brand | Model | Ratio | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Volvo Penta | SX-A | 1.43, 1.51, 1.60, 1.66 | 4-Stroke | 3852045, 3855081 | |
| Volvo Penta | SX-A | 1.79, 1.89, 1.97, 2.18 | 4-Stroke | 3852045, 3855081 | |
| Volvo Penta | DPS-A | 1.68, 1.78, 1.95 | 4-Stroke | 3852045, 3855081 | |
| Volvo Penta | DPS-A | 2.11, 2.14, 2.32 | 4-Stroke | 3852045, 3855081 | |
| Volvo Penta | DPS-B | 1.78, 1.95, 2.14, 2.32 | 4-Stroke | 3852045, 3855081 | |
| Volvo Penta | SX-M | 1.43, 1.51, 1.60, 1.66 | 4-Stroke | 3852045, 3855081 | |
| Volvo Penta | SX-M | 1.79, 1.89, 1.97, 2.18 | 4-Stroke | 3852045, 3855081 | |
| Volvo Penta | SX-MTD | 1.66, 1.79 | 4-Stroke | 3852045, 3855081 | |
| Volvo Penta | SX-C, SX-C1, SX-C2 | Various | 4-Stroke | 3852045, 3855081 | |
| Volvo Penta | SX-R, SX-RT1, SX-RT2, SX-S, SX-ST | Various | 4-Stroke | 3852045, 3855081 | |
| Volvo Penta | DP-G, DP-S1, DP-SM | Various | 4-Stroke | 3852045, 3855081 | Including ratio models 1.68, 1.78, 1.95, 2.32 |
| Volvo Penta | DP-SMTD, DP-SMTD1, DP-SMTD3 | Various | 4-Stroke | 3852045, 3855081 | Including ratio models 1.95, 2.11 |
| Volvo Penta | DPX-A | Various | 4-Stroke | 3852045, 3855081 | |
| Volvo Penta | X-B, X-BLT, XDP-B, XHP-B, XHP-BLT | Various | 4-Stroke | 3852045, 3855081 | |
| Volvo Penta | XXP-A, XXP-ALT, XXP-D3 | Various | 4-Stroke | 3852045, 3855081 |
For Mercury, Mariner, Johnson, Evinrude, and OMC, these seals are used in various gearcase applications.
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Mercury/Mariner | Various | 3.9 - 75 HP | 2-Stroke & 4-Stroke | 25-20633, 25-22174, 25-62704, 25-85148, 802206 | For gearcase assembly parts |
| Johnson/Evinrude | Loopcharged Models | 40-60 HP | 2-Stroke | 303067, 329381, 332584 | 2-cylinder engines |
| Johnson/Evinrude | Loopcharged Models | 60-75 HP | 2-Stroke | 303067, 329381, 332584 | 3-cylinder engines |
| OMC | Cobra | 303067, 3852045 | Upper gear case |
Technical Specs
- Product Type
- Lower Unit O-Ring Seal Kit
- Installation
- Direct fit replacement
- Housing Material
- Rubber
- Housing Color
- Black
- Dimensions
- Dipstick O-Ring: 0.250" (6.35mm) ID × 0.100" (2.54mm) width
- Weight
- 100g (0.22 lb)
- Fitting Type
- O-Ring seals
- Warranty
- 1-year manufacturer warranty against defects
- Other Technical Attributes
- Designed for oil drainage and ventilation system sealing
What’s in the Box
- 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 Notes
- Ensure the engine is off and the sterndrive is trimmed down.
- Place a drain pan under the lower unit.
- Remove the upper vent plug and the lower drain/fill plug.
- Allow the gear oil to drain completely.
- Remove the dipstick if it has a separate o-ring.
- Carefully remove the old o-rings from the plugs and dipstick, cleaning the groove.
- Lightly coat the new o-rings with fresh gear oil.
- Install the new o-rings onto their respective plugs and dipstick.
- Fill the lower unit with the correct gear oil through the bottom hole until it flows from the upper hole.
- Reinstall the upper vent plug, then the lower drain plug. Do not overtighten.
- Check for leaks after a brief run time.
Troubleshooting & FAQ
How do I know if I need to replace my lower unit o-rings?
The most common signs of a failing o-ring are gear oil leaking from the drain, vent, or dipstick plugs, or a milky, emulsified appearance in your gear oil, which indicates water intrusion.
How often should these o-rings be replaced?
It is best practice to replace these o-rings every time you change your sterndrive's gear oil, which is typically recommended annually or every 100 hours of operation, whichever comes first.
Will this kit fit models not listed in the compatibility chart?
While this kit covers a wide range of models, it is critical to confirm fitment using your OEM part number. If your model is not listed, do not assume compatibility. Cross-reference part numbers from your service manual to be sure.
Is any sealant required with these o-rings?
No, additional sealant is generally not required and not recommended. The o-rings are designed to create a seal on their own. Applying a thin coat of fresh gear oil is sufficient to aid installation and prevent pinching.
What is the difference between the dipstick and drain plug o-rings?
In this specific kit, the dipstick o-ring (replaces 3852045) may have different dimensions from the vent and drain plug o-rings (replaces 3855081). Always match the correct o-ring to its corresponding plug.
What happens if I overtighten the plugs?
Overtightening can crush or tear the o-ring, leading to a failed seal. It can also damage the threads in the aluminum gearcase. Tighten the plugs until they are snug, as specified in your engine's service manual.
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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