Yamaha Powerhead Piston Kit, 2-Ring – Fits Yamaha 40-50hp 3-Cylinder Outboards
Yamaha Powerhead Piston Kit, 2-Ring – Fits Yamaha 40-50hp 3-Cylinder Outboards 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 Yamaha Powerhead Piston Kit is designed for Yamaha 40-50hp, 3-cylinder, 2-stroke outboard engines manufactured between 1984 and 1994. The newer 2-ring design serves as a direct replacement for the original 3-ring pistons found in 1984–1988 engines, offering updated performance and reliability.
It provides a direct interchange for Yamaha OEM part numbers 6H4-11636-00-00, 6H4-11636-09-00, 6H4-11631-01-95, 6H4-11635-01-00, and 6H4-11636-01-00, as well as aftermarket equivalent WSM 100-252.
- Installation Method: Direct Replacement
- Piston Design: Modern 2-ring design replaces original 3-ring pistons
- Included Essentials: Kit contains piston, rings, wrist pin, and clips for a complete installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 6H4-11636-00-00 |
| Yamaha | 6H4-11636-09-00 |
| Yamaha | 6H4-11631-01-95 |
| Yamaha | 6H4-11635-01-00 |
| Yamaha | 6H4-11636-01-00 |
| WSM | 100-252 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This piston kit is compatible with the following Yamaha outboard models. Note that the 2-ring piston design replaces the original 3-ring pistons used in 1984–1988 engines.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 40hp | 40 | 2-Stroke | 1984–1994 | 6H4-11636-00-00 | Original 1984-88 engines had 3-ring pistons |
| Yamaha | 50hp | 50 | 2-Stroke | 1984–1994 | 6H4-11636-00-00 | Original 1984-88 engines had 3-ring pistons |
| Yamaha | C40 | 40 | 2-Stroke | 1997–2003 | 6H4-11636-00-00 | 2-ring design |
| Yamaha | C50 | 50 | 2-Stroke | 1998–2001 | 6H4-11636-00-00 | 2-ring design |
Technical Specs
- Product Type
- Piston Kit
- Installation
- Direct Replacement
- Fuel Type
- Gasoline
- Housing Material
- Cast Aluminum
- Dimensions
- Height: 8.0 in; Width: 7.5 in; Length: 8.2 in
- Standard Bore
- 2.638" (67.01mm)
- Piston Design
- 2-ring design (replaces original 3-ring pistons)
What’s in the Box
- 1 x Piston (Replaces 6H4-11636-00-00)
- 1 x Set Piston Rings (Riken brand)
- 1 x Wrist Pin
- 2 x Clips
Installation Notes
- Disconnect the battery and all fuel lines for safety.
- Remove the engine cowling and cylinder head cover.
- Carefully detach the cylinder head and remove the old gasket.
- Rotate the crankshaft to access and remove the old piston and connecting rod assembly.
- Thoroughly clean the cylinder bore and inspect for any wear, scoring, or damage. Hone if necessary.
- Assemble the new piston, rings, wrist pin, and clips onto the connecting rod, ensuring correct orientation.
- Generously lubricate the new piston assembly and cylinder bore with fresh 2-stroke engine oil.
- Carefully guide the new piston assembly into the cylinder using a ring compressor tool.
- Reinstall the cylinder head with a new gasket, torquing all bolts to the manufacturer’s specifications.
- Reassemble all remaining components in the reverse order of removal.
- Once fully assembled, perform a compression test to verify correct installation before starting the engine.
Troubleshooting & FAQ
What's the difference between this 2-ring piston and the original 3-ring version?
This kit features a newer 2-ring piston design, which serves as a direct, more modern replacement for the original 3-ring pistons found in 1984–1988 engines, offering improved sealing and performance.
How do I confirm this piston kit fits my Yamaha outboard?
This kit is designed for specific Yamaha 40-50hp, 3-cylinder, 2-stroke models from 1984–1994. Please refer to the detailed "Engine & Model Compatibility" table on this page to verify your exact model and year range.
Is this piston kit available in different sizes?
Yes. In addition to the standard bore size of 2.638" (67.01mm), this piston kit is also available in multiple oversizes (.010", .020", .030", and .040") to accommodate rebored cylinders. Ensure you order the correct size for your engine's needs.
What are common symptoms of a worn or failed piston?
Signs that you may need to replace your piston include a noticeable loss of engine power, poor compression, an increase in engine noise (like rattling or "piston slap"), excessive blue or white smoke from the exhaust, or the presence of metal shavings in the engine oil.
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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