Upper Casing Gasket – Fits Yamaha 25Q, 40, 50 Series Outboards (Replaces 6H4-45113-00, 6H4-45113-A0-00)
Upper Casing Gasket – Fits Yamaha 25Q, 40, 50 Series Outboards (Replaces 6H4-45113-00, 6H4-45113-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 is a high-quality aftermarket Upper Casing Gasket – Fits Yamaha 25Q, 40, 50 Series Outboards, specifically engineered for various Yamaha 2-Stroke outboard models including the 25Q, 40HP (N/H/E/V/T/Y), and 50HP (D/H/T) series produced between 1984 and 1996.
It serves as a direct replacement for Yamaha OEM part numbers 6H4-45113-00-00 and 6H4-45113-A0-00.
- Installation Location: Serves as the base gasket for the cylinder head.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By | Notes |
|---|---|---|---|
| Yamaha | 6H4-45113-00-00 | 6H4-45113-A0-00 | Original part number. |
| Yamaha | 6H4-45113-A0-00 | Current, updated OEM part number. |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Yamaha owners: Please verify your engine's model, year, and serial prefix (where applicable) to ensure an exact fit.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 25Q (61C) | 25 | 2-Stroke | 1990–1991 | 6H4-45113-A0-00 | |
| Yamaha | 40N | 40 | 2-Stroke | 1984 | 6H4-45113-00-00/A0-00 | Original superseded by A0 version |
| Yamaha | 40H | 40 | 2-Stroke | 1985–1991 | 6H4-45113-00-00/A0-00 | Original superseded by A0 version |
| Yamaha | 40E | 40 | 2-Stroke | 1986 | 6H4-45113-00-00/A0-00 | Original superseded by A0 version |
| Yamaha | 40HE | 40 | 2-Stroke | 1993 | 6H4-45113-A0-00 | |
| Yamaha | 50ETN (6H5) | 50 | 2-Stroke | 1984 | 6H4-45113-00-00/A0-00 | Original superseded by A0 version |
| Yamaha | 50D (6H5) | 50 | 2-Stroke | 1985–1991 | 6H4-45113-00-00/A0-00 | Original superseded by A0 version |
| Yamaha | 50DE (6H5) | 50 | 2-Stroke | 1993 | 6H4-45113-A0-00 |
Technical Specs
- Product Type
- Upper Casing Gasket
- Installation
- Base Gasket for Cylinder Head
- Dimensions
- 310 mm × 210 mm × 3 mm (31.0 cm × 21.0 cm × 0.3 cm)
- Weight
- 0.07 kg (0.15 lb)
- OEM Cross-Reference
- Yamaha 6H4-45113-00-00, 6H4-45113-A0-00
What’s in the Box
- 1 x Upper Casing Gasket (Replaces 6H4-45113-A0-00)
Installation Notes
- Ensure the engine is off and disconnected from the power source.
- Disassemble engine components as required by your service manual to access the upper casing.
- Carefully remove the old gasket, ensuring both mating surfaces are completely clean of any residue, oil, or old gasket material. Use a plastic scraper to avoid gouging the metal surfaces.
- Position the new gasket onto the clean, dry surface. Ensure all bolt holes and passages are perfectly aligned.
- Reassemble the components, tightening bolts in the sequence and to the torque values specified in your engine's service manual.
- After reassembly, check for any fluid leaks before and during initial engine operation.
Troubleshooting & FAQ
How do I know if this gasket fits my specific Yamaha outboard?
This gasket fits a range of Yamaha 25, 40, and 50 HP 2-stroke models from approximately 1984–1996. The best way to confirm is to check the Engine & Model Compatibility table and match your engine's model and year. Verifying the OEM part number (6H4-45113-00 or 6H4-45113-A0) against your service manual is also highly recommended.
Do I need to use gasket sealant with this part?
As a general rule, this type of gasket is designed to be installed dry. Applying sealant can sometimes cause it to slip or fail. Always follow the specific instructions in your outboard's official service manual for the final word on sealant use.
What are the signs that my original upper casing gasket is failing?
Common signs include visible water or oil leaks around the upper casing, engine overheating, an unexplained loss of compression, or a milky appearance in the engine oil, which indicates water intrusion.
What is the difference between part numbers 6H4-45113-00-00 and 6H4-45113-A0-00?
The part number 6H4-45113-A0-00 is a direct supersession for the original 6H4-45113-00-00. This means it is the updated version from Yamaha and is fully interchangeable and backward-compatible.
What is the difference between an OEM and an aftermarket part?
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.
How fast is shipping and what does it cost?
We ship worldwide quickly—typical transit time is 5–15 days. Standard shipping is free to most regions; expedited options may appear at checkout where available for your location.
What is the warranty and return policy?
This part is covered by a 1-year warranty against manufacturing defects under normal use. If you encounter an issue, please 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 purchase.
- This is an aftermarket replacement part, not an original equipment manufacturer (OEM) component.
- Professional installation is recommended for safety and optimal performance.
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
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