Yamaha Piston Kit STD 82mm – Fits Yamaha 48-90HP 2-Stroke Engines (Replaces 688-11631-02-95, 688-11631-02-96)
Yamaha Piston Kit STD 82mm – Fits Yamaha 48-90HP 2-Stroke Engines (Replaces 688-11631-02-95, 688-11631-02-96) 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).
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Product Details
This aftermarket Yamaha Piston Kit STD 82mm is engineered for a precise fit in Yamaha 2-cylinder 48-55HP (1989–2000) and 3-cylinder 75-90HP (1984–2009) 2-stroke engines. It is also compatible with specific Mercury/Mariner 55HP 2-stroke models manufactured between 1990 and 1992.
The kit provides a direct interchange for Yamaha OEM parts 688-11631-02-95, 688-11631-02-96, and 688-11631-03-94, as well as Mercury/Mariner part numbers 761-9276M and 9276M.
- Installs in the engine powerhead.
- Designed for gasoline-fueled 2-stroke outboards.
- Complete kit includes the piston, rings, wrist pin, and circlips.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number | Notes |
|---|---|---|
| Yamaha | 688-11631-02-95 | |
| Yamaha | 688-11631-02-96 | |
| Yamaha | 688-11631-03-94 | |
| Mercury/Mariner | 761-9276M | |
| Mercury/Mariner | 9276M |
Engine & Model Compatibility
Confirm your engine model and year in the table below to ensure correct fitment.
For Yamaha Owners: This piston fits a wide range of 2-cylinder (48/55HP) and 3-cylinder (75/85/90HP) 2-stroke outboards.
For Mercury/Mariner Owners: This part is confirmed for 55HP 2-stroke models from 1990–1992 that use the 761-9276M or 9276M part numbers.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 55BET | 55 | 2-Stroke | 1990 | 688-11631-02-95 | |
| Yamaha | 55BE | 55 | 2-Stroke | 1992 | 688-11631-02-95 | |
| Yamaha | 48 | 48 | 2-Stroke | 1995–2000 | 688-11631-02-95/688-11631-02-96 | 2-Cylinder engine |
| Yamaha | 55 | 55 | 2-Stroke | 1989–1996 | 688-11631-02-95/688-11631-02-96 | 2-Cylinder engine |
| Yamaha | 75 | 75 | 2-Stroke | 1994–2000 | 688-11631-02-95/688-11631-02-96 | 3-Cylinder engine |
| Yamaha | 85 | 85 | 2-Stroke | 1989–1996 | 688-11631-02-95/688-11631-02-96 | 3-Cylinder engine |
| Yamaha | 90 | 90 | 2-Stroke | 1984–2009 | 688-11631-02-95/688-11631-02-96 | 3-Cylinder engine |
| Mercury/Mariner | 55BET | 55 | 2-Stroke | 1990 | 761-9276M, 9276M | |
| Mercury/Mariner | 55BE | 55 | 2-Stroke | 1992 | 761-9276M, 9276M |
Technical Specs
- Product Type
- Piston Kit
- Installation
- Engine Powerhead
- Fuel Type
- Gasoline (2-Stroke)
- Housing Material
- Aluminum Alloy
- Dimensions
- 82mm (3.228") Bore Diameter × 78mm Height
- Weight
- 550g (1.21 lbs)
- Wrist Pin Diameter
- 20mm
- Other Technical Attributes
- Standard (STD) size piston for original bore diameter
What’s in the Box
- 1 x Piston (Replaces 688-11631-03-94/688-11631-02-95/688-11631-02-96)
- 2 x Piston Ring (Replaces 688-11603-A0)
- 2 x Circlip (Replaces 688-11634-00)
- 1 x Piston Pin (Replaces 663-11633-00)
Installation Notes
- Ensure the engine is off, cool, and disconnected from the battery and fuel supply.
- Drain engine fluids and remove the cylinder head and gasket.
- Carefully rotate the crankshaft to access and unbolt the connecting rod cap.
- Gently push the old piston assembly out through the top of the cylinder.
- Thoroughly clean the cylinder walls, crankshaft, and connecting rod surfaces of any carbon buildup or debris.
- Install the new piston rings onto the new piston, checking for correct alignment and gap orientation.
- Attach the piston to the connecting rod with the new wrist pin and circlips, ensuring they are fully seated.
- Generously lubricate the cylinder walls, piston, and rings with fresh 2-stroke engine oil.
- Use a piston ring compressor to carefully guide the new piston assembly back into the cylinder bore.
- Reinstall the connecting rod cap, torquing the bolts to the manufacturer’s specifications.
- Reassemble the remaining components (cylinder head, gasket, etc.) using new gaskets where required.
- After reassembly, perform a proper engine break-in procedure to ensure components seat correctly.
Troubleshooting & FAQ
How do I know if this piston kit fits my engine?
The best way to confirm fitment is by matching your engine's model and year to the compatibility table. You should also verify that your engine's original piston carries one of the part numbers listed in our Part Number Matrix, such as 688-11631-02-95 for Yamaha or 761-9276M for Mercury/Mariner.
What does "Standard (STD)" size mean?
A Standard (STD) size piston is designed to fit an engine block with its original, factory-sized cylinder bore. It is not oversized. If your cylinder has been machined or bored out during a previous rebuild, you will need an oversized piston, not this STD one.
What are the signs of a worn or failed piston?
Common symptoms include loss of compression, excessive blue or white smoke from the exhaust, a knocking or rattling sound from the engine (piston slap), and poor overall performance or difficulty starting. These signs indicate internal engine wear and should be diagnosed by a professional.
Does the cylinder bore need to be honed before installing this new piston?
Yes, it is highly recommended to have the cylinder bore lightly honed by a machine shop before installing a new piston. Honing creates a cross-hatch pattern on the cylinder walls that helps the new piston rings seat properly, ensuring optimal compression and oil control.
Can I reuse my old wrist pin or circlips?
No. This kit includes a new piston pin and new circlips. These are critical components that experience high stress. For a reliable and safe repair, you should always use the new hardware provided in the kit.
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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