Piston Ring Kit (0.50mm) – Fits Yamaha 40HP 2-Stroke Outboards (Replaces 6F5-11610-20)
Piston Ring Kit (0.50mm) – Fits Yamaha 40HP 2-Stroke Outboards (Replaces 6F5-11610-20) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Piston Ring Kit (0.50mm) – Fits Yamaha 40HP 2-Stroke Outboards (Rep...
Product Details
This is a 0.50mm oversize Piston Ring Kit (0.50mm) – Fits Yamaha 40HP 2-Stroke Outboards (Replaces 6F5-11610-20), specifically designed for Yamaha 40HP 2-stroke outboard motors, including C40, E40GMH, and 40GWH models. It's engineered for pistons with a 78.5mm diameter requiring a 0.50mm oversize.
This kit serves as a direct replacement for Yamaha part numbers 6F5-11610-20, 6F51161020, 6F6-11610-20, and 6F61161020.
- Manufactured from high-quality steel for durability and longevity.
- Engineered as a 0.50mm oversize kit for bored or worn cylinders.
- Includes a complete ring set for a single piston assembly.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 6F5-11610-20 |
| Yamaha | 6F51161020 |
| Yamaha | 6F6-11610-20 |
| Yamaha | 6F61161020 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This part is compatible with the following Yamaha outboard models:
| Brand | Model | Rated HP | Stroke | OEM Part No. |
|---|---|---|---|---|
| Yamaha | C40 | 40 | 2-Stroke | 6F5-11610-20 |
| Yamaha | E40GMH | 40 | 2-Stroke | 6F5-11610-20 |
| Yamaha | 40GWH | 40 | 2-Stroke | 6F5-11610-20 |
Technical Specs
- Product Type
- Piston Ring Kit
- Ring Size
- 0.50mm Oversize
- Piston Diameter
- 78.5mm
- Application
- 2-Stroke Marine Outboard Engines
- Engine Type
- 2-Stroke
- Compatibility
- Yamaha 40HP Outboard Engines
- Material
- High-Quality Steel
- OEM Replacement
- Yes
- Package Contents
- Complete Ring Set
- Box Dimensions
- 8.5" L x 8.5" W x 1.0" H
What’s in the Box
- 1 x Piston Ring Set (for one piston)
Installation Notes
- Carefully clean the piston grooves, removing all carbon buildup and debris before installing the new rings.
- Use a dedicated piston ring expander tool to gently fit each ring into its groove. Avoid over-stretching the rings.
- Install the rings in the correct order, typically starting with the oil control ring at the bottom, followed by the scraper ring, and finally the top compression ring.
- Ensure any markings on the rings face upwards towards the top of the piston as per your engine's service manual.
- Stagger the ring end gaps according to the manufacturer's specifications to prevent compression loss.
- Thoroughly lubricate the piston, rings, and cylinder wall with fresh 2-stroke engine oil before reassembly.
Troubleshooting & FAQ
How do I know if I need 0.50mm oversize rings?
Oversize rings are used when a cylinder has been bored or honed beyond its standard diameter during a rebuild. Measure your cylinder bore with a precision tool. If it matches the 0.50mm oversize specification (standard 78.0mm + 0.50mm), this kit is appropriate. Standard-size rings will not seal properly in an oversized cylinder.
What are the signs of failing piston rings?
Common symptoms include excessive blue or white smoke from the exhaust, a noticeable loss of engine power, increased oil consumption, and poor results from a cylinder compression test. These indicate that combustion gases are blowing by the rings or oil is seeping past them into the combustion chamber.
Does this kit contain rings for all pistons in my engine?
No, this package contains a complete ring set for a single piston. If you are rebuilding an engine with multiple cylinders, you will need to purchase one kit per piston.
Why is ring gap orientation important?
The gaps at the ends of the piston rings must be staggered (often 120 or 180 degrees apart) around the piston. Aligning the gaps would create a direct path for combustion gases to escape, resulting in a significant loss of compression and engine power. Always consult your service manual for the correct orientation.
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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