0.50mm Oversize Piston – Fits Yamaha/Parsun 25-30HP 2-Stroke Outboards
0.50mm Oversize Piston – Fits Yamaha/Parsun 25-30HP 2-Stroke Outboards is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
0.50mm Oversize Piston – Fits Yamaha/Parsun 25-30HP 2-Stroke Outboards
Product Details
This is a 0.50mm Oversize Piston kit designed for a range of Yamaha and Parsun 25-30HP 2-stroke outboard engines. It fits various Yamaha 25HP and 30HP models manufactured between 1996 and 2012, including the B, BMH, BWH, VE, VM, G, GE, H, and C series. It is also compatible with Yamaha-based Parsun 25HP and 30HP 2-stroke models.
This assembly serves as a direct replacement for Yamaha OEM part numbers 61N-11636-00-00, 61N-11636-00, and 61N-11636-00K, and interchanges with Asaki 61N-11636-00 and SAIL MARINE 61N-11636-00-00.
- Installs as a direct replacement for worn or damaged factory pistons.
- Engineered for use in 2-stroke gasoline marine environments.
- The kit includes the piston, piston pin, rings, and circlips for a complete installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 61N-11636-00-00 |
| Yamaha | 61N-11636-00 |
| Yamaha | 61N-11636-00K |
| Asaki | 61N-11636-00 |
| SAIL MARINE | 61N-11636-00-00 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This piston fits a wide range of Yamaha 25HP and 30HP 2-stroke models from the mid-1990s through 2012. Please verify your specific model and year.
For Parsun engines, this component is compatible with T25 and T30 2-stroke models of all years, reflecting their design basis on Yamaha counterparts.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 25B/BMH/BWH | 25 | 2-Stroke | 2001–2010 | 61N-11636-00-00 | |
| Yamaha | 25VE/VM | 25 | 2-Stroke | 1996–2001 | 61N-11636-00-00 | |
| Yamaha | E25A/BMH/HMH | 25 | 2-Stroke | 2001–2012 | 61N-11636-00-00 | |
| Yamaha | 30G/GE | 30 | 2-Stroke | 1996–2000 | 61N-11636-00-00 | |
| Yamaha | 30H/HMH/HWC | 30 | 2-Stroke | 1996–2012 | 61N-11636-00-00 | |
| Yamaha | E30HMH/HW | 30 | 2-Stroke | 2003–2012 | 61N-11636-00-00 | |
| Yamaha | C30ELRT/ELRV/MLHS/ELRU/ERT/ELRS/ELRR | 30 | 2-Stroke | 1996–2008 | 61N-11636-00-00 | Per Ebay listing |
| Parsun | T25/T30 | 25-30 | 2-Stroke | All years | 61N-11636-00-00 | Aftermarket compatibility |
Technical Specs
- Product Type
- Piston (0.50mm Oversize)
- Installation
- Direct replacement
- Fuel Type
- Gasoline (2-stroke)
- Material
- Aluminum alloy
- Dimensions
- 3.38" x 3.38" x 3.38"
- Oversize
- 0.50mm (0.020")
- Ring Package
- Included
- Pin
- Included
- Clips
- Included
What’s in the Box
- 1 x Piston (61N-11636-00-00)
- 1 x Piston Pin
- 1 x Set of Piston Rings
- 2 x Circlips
Installation Notes
- Disconnect the battery and ensure the engine is cool. Drain the engine oil and coolant.
- Remove the engine cover and disconnect any components obstructing access to the cylinder head, such as the fuel lines and electrical connections.
- Carefully remove the cylinder head bolts in the sequence specified by the manufacturer's service manual to prevent warping. Lift the head off the engine block.
- Rotate the crankshaft to bring the piston to the bottom of its travel. Inspect the cylinder wall for damage or scoring.
- Remove the old piston pin clips, then carefully push out the piston pin to disconnect the piston from the connecting rod.
- Clean the cylinder bore, connecting rod, and all mating surfaces of any carbon buildup or old gasket material.
- Lubricate the new piston and rings with 2-stroke engine oil. Install the rings onto the new piston, ensuring they are oriented correctly.
- Attach the new piston to the connecting rod with the new pin and secure it with the new circlips.
- Using a ring compressor, gently guide the piston into the cylinder bore.
- Reinstall the cylinder head with a new gasket, torquing the bolts to the manufacturer’s specification in the correct sequence.
- Reassemble all previously removed components, refill fluids, and reconnect the battery.
- Before starting, manually turn the crankshaft a few times to ensure everything moves smoothly. Start the engine and check for leaks or unusual noises.
Troubleshooting & FAQ
How do I know if I need an oversize piston?
An oversize piston is required when the cylinder bore has been machined (honed or bored) to correct for wear, tapering, or out-of-round conditions. You must measure the cylinder's internal diameter with a precision tool. This 0.50mm oversize piston is for cylinders that have been bored 0.50mm larger than the standard size.
Do I need to modify my engine cylinder for this piston?
Yes. This is an oversize piston. It is designed to be used only after your engine cylinder has been professionally machined (bored) to precisely 0.50mm over the standard diameter. Installing it in a standard, non-machined cylinder will result in immediate engine damage.
What are the common signs of a failing piston or worn rings?
Symptoms include low compression, excessive blue or white smoke from the exhaust, a noticeable loss of power, increased oil consumption, and a rattling or knocking sound from within the engine.
Is this piston compatible with ethanol-blended fuels?
This piston is made from a durable aluminum alloy suitable for modern gasoline, including fuels with standard ethanol blends (up to E10). However, always follow your outboard manufacturer's fuel recommendations for best performance and engine 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.
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