Gasket – Fits OMC Johnson Evinrude (Replaces 0303339)
Gasket – Fits OMC Johnson Evinrude (Replaces 0303339) is backordered and will ship as soon as it is back in stock.
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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.).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Gasket – Fits OMC Johnson Evinrude (Replaces 0303339)
Product Details
This high-quality aftermarket Gasket – Fits OMC Johnson Evinrude (Replaces 0303339) is designed for a precise seal between the bearcase and bearing housing. It is engineered for OMC, Johnson, and Evinrude 6 HP to 9.9 HP 2-stroke outboard models, including 1968 and other vintage engines.
This gasket serves as a direct interchange for OMC part 0303339, Johnson Evinrude 303339/0303339, Sierra 18-2891, and GLM 34040.
- Installs between the bearcase and bearing housing.
- Engineered to withstand demanding marine environments.
- Provides a reliable seal to prevent lubricant leaks and water intrusion.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| OMC | 0303339 |
| Johnson Evinrude | 303339 / 0303339 |
| Sierra | 18-2891 |
| GLM | 34040 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Evinrude, Johnson, and OMC owners, please verify your engine's horsepower, model, and year against the specifications listed here to ensure correct fitment.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Evinrude | 6 HP | 6 | 2-Stroke | 1968 | 0303339 | Gearcase Group |
| Johnson | 6 HP | 6 | 2-Stroke | 1968 | 0303339 | Gearcase Group |
| Evinrude | 9.5 HP | 9.5 | 2-Stroke | Vintage Engines | 0303339 | Gasket, Bearcase to Bearing Housing |
| Johnson | 9.5 HP | 9.5 | 2-Stroke | Vintage Engines | 0303339 | Gasket, Bearcase to Bearing Housing |
Technical Specs
- Product Type
- Gasket
- Installation
- Bearcase to Bearing Housing
- Dimensions
- 4.0" x 5.13" x 1.06"
- Weight
- 0.02 lbs (0.009 kg)
- Warranty
- Limited Lifetime (Sierra)
What’s in the Box
- 1 x Gasket, bearcase to bearing housing (0303339 / 303339)
Installation Notes
- Ensure the engine is off, cool, and disconnected from the power source before starting.
- Drain the gearcase lubricant completely into an approved container.
- Disassemble the lower unit to gain access to the bearcase and bearing housing junction.
- Carefully remove the old, worn gasket. Thoroughly clean both mating surfaces of any old gasket material or residue, being careful not to gouge the metal.
- Position the new gasket onto the cleaned surface, ensuring it aligns with all bolt holes and passages.
- Reassemble the components, tightening the fasteners to the manufacturer-specified torque in the recommended sequence to ensure an even seal.
- Refill the gearcase with new, correct-grade lubricant.
- After reassembly, check for any leaks around the newly installed gasket before operating the vessel in water.
Troubleshooting & FAQ
How do I know if this gasket will fit my engine?
This gasket is specifically designed for OMC, Johnson, and Evinrude 6 HP (1968) and 9.5 HP ("Vintage") 2-stroke models. To ensure a perfect match, please compare your existing part number to the equivalents listed in our Part Number Matrix (0303339, 18-2891) and check the Engine & Model Compatibility table.
What are the signs of a failed bearcase gasket?
The most common symptoms of a failing gasket in this location are milky or creamy-looking gear lubricant (indicating water intrusion) or a visible oil leak from the lower unit. This compromises gear protection and requires immediate attention.
Should I use sealant or adhesive with this gasket?
Generally, these gaskets are designed to be installed dry. However, it is essential to consult your specific engine's official service manual, as some models or conditions may call for a light application of a specific non-hardening sealant.
What is the difference between this part and the OEM version?
There is no functional difference. This is a high-quality aftermarket part manufactured to meet or exceed OEM specifications for fit, form, and material performance, offering a reliable and cost-effective alternative.
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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