Upper Casing Gasket – Fits Yamaha 25/30HP (Replaces 6J8-45113-00-00/6J8-45113-A0-00)
Upper Casing Gasket – Fits Yamaha 25/30HP (Replaces 6J8-45113-00-00/6J8-45113-A0-00) is backordered and will ship as soon as it is back in stock.
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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
Product Details
This replacement Upper Casing Gasket provides a direct fit for select Yamaha 25HP and 30HP 2-stroke outboard engines manufactured between 1986 and 1995. It is designed to create a reliable seal at the power head base assembly, preventing leaks and ensuring proper engine compression.
This gasket directly replaces Yamaha OEM part numbers 6J8-45113-00-00 and 6J8-45113-A0-00.
- Installs at the power head base.
- Engineered to meet or exceed original equipment specifications.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By | Notes |
|---|---|---|---|
| Yamaha | 6J8-45113-00-00 | 6J8-45113-A0-00 | Original part number. |
| Yamaha | 6J8-45113-A0-00 | Current replacement part. |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This gasket is specifically designed for certain Yamaha 25HP and 30HP 2-stroke models. Check your engine's part number or serial to ensure a match.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 25J | 25 | 2-Stroke | 1987–1991 | 6J8-45113-A0-00 | Supersedes 6J8-45113-00-00 |
| Yamaha | 25JEO | 25 | 2-Stroke | 1991 | 6J8-45113-A0-00 | Supersedes 6J8-45113-00-00 |
| Yamaha | 30D | 30 | 2-Stroke | 1986–1995 | 6J8-45113-A0-00 | Supersedes 6J8-45113-00-00 |
| Yamaha | 30DM | 30 | 2-Stroke | 1994 | 6J8-45113-A0-00 | Supersedes 6J8-45113-00-00 |
Technical Specs
- Product Type
- Upper Casing Gasket
- Installation
- Power Head Base Assembly
- Dimensions
- 25.5 cm x 14.6 cm x 0.3 cm
What’s in the Box
- 1 x Upper Casing Gasket (6J8-45113-A0-00)
Installation Notes
- Ensure the engine is off, cool, and disconnected from the battery.
- Remove the engine cowling and any components obstructing access to the power head.
- Carefully unbolt and remove the power head from the upper casing, taking care not to damage other components.
- Peel off the old gasket and meticulously clean both mating surfaces. Use a plastic scraper and appropriate solvent to remove all residue and oil.
- Place the new gasket into position, ensuring it aligns with all bolt holes and passages.
- Reinstall the power head, tightening bolts in the sequence and to the torque specified in your engine's service manual.
- Reconnect all components and check for leaks before returning to service.
Troubleshooting & FAQ
How do I know if this gasket will fit my Yamaha engine?
This gasket is specifically for Yamaha 25HP (25J, 25JEO) and 30HP (30D, 30DM) 2-stroke models from approximately 1986 to 1995. The best way to confirm fitment is to check your engine's model and year against the compatibility list or match the part number (6J8-45113-A0-00 or 6J8-45113-00-00) from your service manual.
What are the signs of a failed upper casing gasket?
A bad gasket can cause several issues, including visible water or oil leaks around the seam of the power head base, engine overheating due to water passage blockage, or a loss of power and compression.
Is part 6J8-45113-A0-00 the same as 6J8-45113-00-00?
Yes. The part number 6J8-45113-A0-00 is the newer, official replacement that supersedes the older 6J8-45113-00-00 part. They are interchangeable, and this listing provides the current version.
Should I use sealant or adhesive with this gasket?
In most cases, this gasket is designed to be installed dry on properly cleaned and prepared surfaces. However, always refer to your specific engine's official service manual for Yamaha's recommendations on using sealant for this application.
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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