Piston Kit – Fits Yamaha 25-30 HP Outboard Engines (Replaces 61N-11635-00)
Piston Kit – Fits Yamaha 25-30 HP Outboard Engines (Replaces 61N-11635-00) 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 an aftermarket Piston Kit – Fits Yamaha 25-30 HP Outboard Engines (Replaces 61N-11635-00), designed for various 2-stroke models manufactured between 1996 and 2010. It is compatible with engine models including the 25VE/VM, 25B/BMH, 30G/GE, and E30HMH series. This kit serves as a 0.25 mm oversize replacement, ideal for engines requiring a cylinder bore-out.
This component is a direct interchange for OEM part numbers 61N-11635-00 and 61N-11635-00-00, as well as the aftermarket equivalent Wiseco WIS-3188PS.
- Engineered as a 0.25mm oversize piston for rebuilt or bored engine cylinders.
- Constructed from durable aluminum alloy for reliable performance.
- Includes all essential components for a complete piston replacement: piston, rings, wrist pin, and clips.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Yamaha | 61N-11635-00-00 | OEM |
| Yamaha | 61N-11635-00 | OEM |
| Wiseco | WIS-3188PS | Aftermarket |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Yamaha engines, please verify your specific model and production year before ordering.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 25VE/VM | 25 | 2-Stroke | 1996–2001 | 61N-11635-00 | 0.25mm oversize version |
| Yamaha | 25B/BMH | 25 | 2-Stroke | 2001–2010 | 61N-11635-00 | 0.25mm oversize version |
| Yamaha | 30G/GE | 30 | 2-Stroke | 1996–2000 | 61N-11635-00 | 0.25mm oversize version |
Technical Specs
- Product Type
- Piston Kit
- Weight
- 0.82-0.86 lb (0.37-0.39 kg)
- Product Dimensions
- 3.38 in x 3.38 in x 3.38 in
- Piston Bore Size (Standard)
- 67.0 mm (2.638 in)
- Piston Bore Size (Oversize)
- 67.25 mm (2.648 in)
- Housing Material
- Aluminum alloy
- Package Contents
- Piston, piston rings, wrist pin, pin clips
- Compatibility
- 25HP 2-stroke 1996–2010, 30HP 2-stroke 1996–2000
- Other Technical Attributes
- 0.25 mm oversize version (original part number 61N-11635-00)
What’s in the Box
- 1 x Piston
- 1 x Set of Piston Rings
- 1 x Wrist Pin
- 2 x Pin Clips
Installation Notes
- Disconnect the battery and ensure the fuel supply is shut off.
- Drain the engine oil and coolant completely.
- Remove the cylinder head and any other components blocking access to the piston.
- Carefully extract the old piston, wrist pin, and rings.
- Thoroughly clean the cylinder walls and inspect for any scoring or damage. Verify cylinder measurements before proceeding.
- Properly gap and install the new piston rings onto the new piston.
- Generously lubricate the new piston, rings, and cylinder wall with fresh engine oil.
- Install the new piston assembly, ensuring its orientation matches the service manual's instructions.
- Reassemble the engine components in the reverse order of disassembly.
- Torque all fasteners to the manufacturer's specified values. Check for smooth engine rotation by hand before starting.
Troubleshooting & FAQ
How do I know if I need an oversize piston?
This is a 0.25mm oversize piston kit. It is only suitable for engines where the cylinder has been machined (bored out) to accommodate the larger diameter. You must measure your cylinder bore to confirm it matches the 67.25 mm dimension before purchasing. Using this in a standard bore will cause engine seizure.
What are the signs of a failing piston?
Common symptoms include a noticeable loss of compression, increased blue or white smoke from the exhaust, a knocking or slapping sound from within the engine (especially when cold), and a general reduction in power and performance.
Is this kit compatible with 4-stroke Yamaha models?
No. This piston kit is specifically designed for the 2-stroke Yamaha outboard engines listed in the compatibility table. It is not compatible with any 4-stroke models.
What is the OEM vs. Aftermarket difference?
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 certified facility and are batch-inspected for quality and consistency.
What is the shipping speed & cost?
We ship worldwide quickly—typical transit time is 5–15 days. Standard shipping is free to most locations, with expedited options available at checkout where applicable.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal use. If any issues arise, please contact our support team with your order details. Returns are accepted within our standard window for items that are unused and in their 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 compatible—do not purchase.
- This is an aftermarket replacement part, not an OEM component.
- Professional installation is strongly recommended for safety and to ensure proper 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 quality control.
Payment & Security
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