Lower Unit Gearcase Seal Kit – Fits Johnson/Evinrude 20-35 HP (Replaces 396351, 87680, 18-2658)
Lower Unit Gearcase Seal Kit – Fits Johnson/Evinrude 20-35 HP (Replaces 396351, 87680, 18-2658) 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 Gearcase Seal Kit – Fits Johnson/Evinrude 20-35 HP (Repl...
Lower Unit Gearcase Seal Kit – Fits Johnson/Evinrude 20-35 HP (Replaces 396351, 87680, 18-2658) is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket Lower Unit Gearcase Seal Kit is designed for a wide range of Johnson/Evinrude 20, 25, 30, and 35 HP 2-stroke outboard engines manufactured between 1977 and 2005. It provides all the necessary seals and gaskets to service a leaking or damaged lower unit gearcase, restoring watertight integrity and preventing costly gear damage.
This kit serves as a direct replacement for Johnson/Evinrude part number 396351 / 0396351, Sierra 18-2658, GLM 87680, and Mallory 9-74101, ensuring a precise fit and reliable performance.
- Engineered as a direct, model-specific replacement for easy installation.
- Includes a complete set of seals, washers, and O-rings for a comprehensive overhaul.
- Helps prevent water intrusion and oil leaks, protecting internal gearcase components.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number |
|---|---|
| Johnson/Evinrude | 396351 / 0396351 |
| Sierra | 18-2658 |
| GLM | 87680 |
| Mallory | 9-74101 |
Engine & Model Compatibility
Confirm your engine model and year in the table below to ensure correct fitment.
This kit is verified for the following Johnson/Evinrude outboard models.
| Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|
| 20 HP | 20 | 2-Stroke | 1985–1997 | 396351 | |
| 25 HP | 25 | 2-Stroke | 1985–2005 | 396351 | |
| 30 HP | 30 | 2-Stroke | 1985–1998, 2003 | 396351 | |
| 33 HP | 33 | 2-Stroke | 1997 | 396351 | |
| 35 HP | 35 | 2-Stroke | 1987–2001 | 396351 | |
| 200 HP | 200 | 2-Stroke | 1997 | 396351 | Special application |
| 225 HP | 225 | 2-Stroke | 2003 | 396351 | Special application |
Technical Specs
- Product Type
- Lower Unit Gearcase Seal Kit
- Installation
- Direct replacement
- Weight
- Approx. 2.39 oz (67.8 g)
- Warranty
- Manufacturer dependent, typically 1 year
- Other Technical Attributes
- Complete kit includes all necessary seals for gearcase service
What’s in the Box
- 1 x Impeller Plate Gasket
- 1 x Shift Rod Washer
- 2 x Oil Seals (Driveshaft)
- 1 x Oil Seal
- 1 x Oil Seal
- 1 x Oil Seal
- 1 x Oil Seal
- 1 x Rubber Seal
- 2 x Drain/Fill Plug Washers
- 1 x O-Ring
- 2 x O-Ring
- 1 x O-Ring
- 3 x O-Ring
- 2 x O-Ring
- 1 x O-Ring
- 1 x O-Ring
Installation Notes
- Position the engine securely and place a drain pan under the lower unit.
- Remove the lower drain/fill screw and the upper vent screw to drain the gearcase oil completely.
- Disconnect the shift linkage and remove the bolts securing the lower unit to the midsection.
- Carefully lower and remove the gearcase assembly from the engine.
- Disassemble the gearcase to access the propeller shaft, driveshaft, and shift rod seals. A service manual for your specific model is highly recommended.
- Carefully remove all old seals, O-rings, and gaskets, taking care not to scratch the housing surfaces.
- Clean all sealing surfaces thoroughly to remove any old sealant or corrosion.
- Install the new seals and O-rings from the kit, lightly lubricating them with marine grease or clean gear oil.
- Reassemble the gearcase, ensuring all components are torqued to manufacturer specifications.
- Reinstall the lower unit, connect the shift linkage, and refill the gearcase with the correct type and amount of marine gear lubricant.
- Install new washers on the drain and vent plugs, and tighten them securely.
Troubleshooting & FAQ
How do I know if my gearcase seals are failing?
Common signs include milky, cream-colored gear oil (indicating water intrusion) or a visible oil leak around the propeller shaft or drain plugs. You may also find fishing line tangled behind the propeller, which can quickly damage the prop shaft seal.
Why are there "special application" notes for the 200/225 HP models?
While this kit's part number is referenced for some larger V6 models in specific years, it's primarily intended for the 20-35 HP range. The V6 application may only use a portion of the kit or relate to a sub-assembly. Please verify the exact parts required for your V6 engine before ordering.
Why might there be extra O-rings or seals in my kit?
Aftermarket kits are often designed to cover multiple model years or variations that use slightly different components. It is normal to have a few unused parts after a correct installation on your specific engine.
Can I replace just one leaking seal?
While possible, it is best practice to replace all the seals in the gearcase at the same time. If one seal has failed due to age or wear, others are likely to fail soon after. This comprehensive approach prevents repeated disassembly and potential damage.
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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