Piston Ring Set (+0.25mm) – Fits Yamaha 25HP/30HP 2-Stroke Outboard (61N-11604-00-00)
Piston Ring Set (+0.25mm) – Fits Yamaha 25HP/30HP 2-Stroke Outboard (61N-11604-00-00) is backordered and will ship as soon as it is back in stock.
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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).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Product Details
This aftermarket Piston Ring Set (+0.25mm) – Fits Yamaha 25HP/30HP 2-Stroke Outboard (61N-11604-00-00) is designed for specific Yamaha 25HP and 30HP 2-stroke outboard motors requiring an oversize piston ring. It is crucial for engine rebuilds where the cylinder has been bored to +0.25mm over the standard size.
This set serves as a direct replacement for Yamaha OEM part number 61N-11604-00-00 and is an equivalent for Yamaboya part 61N-11604-00.
- Installation: Fits directly onto the engine piston.
- Size Specification: +0.25mm oversize (O/S) for bored cylinders.
- Package Contents: Includes a complete set of 2 piston rings.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 61N-11604-00-00 |
| Yamaboya | 61N-11604-00 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Yamaha owners: This part is known to fit the specific models listed below. Please verify your engine's part requirements as year ranges are not available.
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Yamaha | Outboard | 25 | 2-Stroke | 61N-11604-00-00 | Oversize +0.25mm |
| Yamaha | Outboard | 30 | 2-Stroke | 61N-11604-00-00 | Oversize +0.25mm |
| Yamaha | C30ELRV | 30 | 2-Stroke | 61N-11604-00-00 | Model specifically mentioned in listing |
Technical Specs
- Product Type
- Piston Ring Set
- Installation
- Engine Piston
- Fuel Type
- Gasoline
- Oversize Specification
- +0.25mm (O/S)
- Product Dimensions
- 1.5 in (H) x 7.5 in (W) x 7.5 in (L)
- Fitting Type
- Crankshaft Piston Ring
- Warranty
- 1 Year
- Quantity
- 1 set = 2 pieces
What’s in the Box
- 2 x Piston Ring (+0.25mm) (61N-11604-00-00)
Installation Notes
- Disconnect the battery and ensure the engine is cool before starting work.
- Carefully remove the cylinder head and other components to access the piston.
- Use a piston ring removal tool to take off the old rings. Avoid scratching the piston.
- Thoroughly clean the piston ring grooves to remove carbon deposits and oil residue.
- Install the new piston rings using a ring expander tool, ensuring they are oriented correctly and seated properly in the grooves.
- Lubricate the cylinder walls and new rings with fresh engine oil.
- Use a piston ring compressor to carefully guide the piston back into the cylinder.
- Reassemble the engine components in reverse order, torquing all bolts to manufacturer specifications.
- After reassembly, perform a compression test to confirm proper installation.
Troubleshooting & FAQ
How do I know if I need +0.25mm oversize piston rings?
Oversize piston rings are required after the engine cylinder has been machined or "bored" to correct wear or damage. If your cylinder was bored to 0.25mm over the standard diameter, you must use corresponding +0.25mm oversize rings and pistons. Standard rings will not seal properly in a bored cylinder.
Will these rings fit any Yamaha 25HP or 30HP 2-stroke engine?
While designed for the 25HP and 30HP 2-stroke series, compatibility is determined by the OEM part number (61N-11604-00-00) and the cylinder bore size. Always verify this part number against your engine's service manual before purchasing, especially since specific model years are not provided.
What are the common signs of failing piston rings?
Symptoms of worn or damaged piston rings include excessive blue or white smoke from the exhaust, a noticeable loss of engine power, increased oil consumption, and poor results from a compression test. These signs indicate that combustion gases are blowing past the rings or oil is seeping into the combustion chamber.
Is there a "break-in" period for new piston rings?
Yes, new piston rings require a break-in period to seat properly against the cylinder wall. This typically involves running the engine at varying, moderate RPMs for a few hours. Avoid prolonged idling or full-throttle operation during this time. Consult your engine's service manual for specific break-in procedures.
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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