Piston Kit – Fits Yamaha 40N/E/H & 50D/ETN Outboards (Replaces 6H4-11635-00K)
Piston Kit – Fits Yamaha 40N/E/H & 50D/ETN Outboards (Replaces 6H4-11635-00K) 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 aftermarket Piston Kit – Fits Yamaha 40N/E/H & 50D/ETN Outboards (Replaces 6H4-11635-00K) is designed for compatibility with Yamaha 2-Stroke 40 HP (N/E/H models, 1984–1988) and 50 HP (D/ETN models, 1984–1988) outboard motors. It serves as a high-quality replacement to restore engine performance and reliability.
This kit provides a direct interchange for Yamaha part numbers 6H4-11635-00K, 6H4-11635-00, and 6H4-11635-09.
- Installation: Designed for professional installation as an engine internal component.
- Fuel Compatibility: Engineered for use with gasoline in 2-Stroke engines.
- Quality Construction: Made from durable aluminum alloy to meet or exceed OEM specifications.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By |
|---|---|---|
| Yamaha | 6H4-11635-00 | 6H4-11635-00K |
| Yamaha | 6H4-11635-09 | 6H4-11635-00K |
| Yamaha | 6H4-11635-00K |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 40N | 40 | 2-Stroke | 1984–1988 | 6H4-11635-00K | Supersedes 6H4-11635-00, 6H4-11635-09 |
| Yamaha | 40E | 40 | 2-Stroke | 1984–1988 | 6H4-11635-00K | Supersedes 6H4-11635-00, 6H4-11635-09 |
| Yamaha | 40H | 40 | 2-Stroke | 1984–1988 | 6H4-11635-00K | Supersedes 6H4-11635-00, 6H4-11635-09 |
| Yamaha | 50D | 50 | 2-Stroke | 1984–1988 | 6H4-11635-00K | Supersedes 6H4-11635-00, 6H4-11635-09 |
| Yamaha | 50ETN | 50 | 2-Stroke | 1984–1988 | 6H4-11635-00K | Supersedes 6H4-11635-00, 6H4-11635-09 |
Technical Specs
- Product Type
- Piston Kit
- Installation
- Engine Internal Component
- Fuel Type
- Gasoline (2-Stroke)
- Housing Material
- Aluminum Alloy
- Dimensions
- 8.2" L x 7.5" W x 8.0" H
- Warranty
- Standard manufacturer warranty
- Other Technical Attributes
- High-quality replacement component for maintaining engine performance and reliability
What’s in the Box
- 1 x Piston Kit (6H4-11635-00K)
Installation Notes
- Ensure the engine is off, cool, and disconnected from the battery and fuel supply.
- Drain the engine oil and coolant completely.
- Remove the cylinder head and other necessary components to gain access to the old piston assembly.
- Carefully remove the existing piston, wrist pin, and connecting rod. Note the orientation.
- Thoroughly clean the cylinder walls and inspect for any scoring or damage. Hone the cylinder if necessary.
- Install the new piston rings onto the new piston, following the manufacturer’s specifications for ring gap and orientation.
- Generously lubricate the new piston, rings, and cylinder wall with fresh engine oil.
- Carefully install the new piston assembly into the cylinder, ensuring it is oriented correctly.
- Reassemble all engine components in the reverse order of disassembly.
- Torque all fasteners to the manufacturer's specified values using a torque wrench.
- Refill the engine with the correct type and amount of oil and coolant.
- After reassembly, perform a proper engine break-in procedure to allow the new rings to seat correctly.
Troubleshooting & FAQ
How do I know if this piston kit is correct for my engine?
Verify your engine model and year against the "Engine & Model Compatibility" table. It is also essential to visually compare your old part with our product images to ensure an exact match before ordering.
What are the common signs of a failing piston?
Symptoms of a worn or damaged piston include excessive exhaust smoke, a noticeable loss of power, increased oil consumption, and an audible knocking or "slapping" sound from the engine, especially when cold.
Do I need to replace other parts when installing a new piston?
Yes, it is best practice to also replace the piston rings, wrist pin, and circlips, which are included in this kit. You should also inspect the cylinder walls, connecting rod, and associated bearings for wear and replace them if they are out of specification.
What is the correct break-in procedure for a new piston?
Proper break-in is crucial. After installation, operate the engine under light load with varied RPMs for the first few hours. Avoid sustained high speeds or heavy loads to allow the new piston rings to seat properly against the cylinder wall for optimal compression and longevity.
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.
Payment & Security
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