Piston Kit – Fits Yamaha 25-30 HP Outboard Engines (Replaces 689-11631-00-95)
Piston Kit – Fits Yamaha 25-30 HP Outboard Engines (Replaces 689-11631-00-95) 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 Piston Kit – Fits Yamaha 25-30 HP Outboard Engines is designed for Yamaha 25 HP 2-Stroke (1985) and 30 HP 2-Stroke (1984–1992) models, including 30A, C30, and CV30 variants. It also fits Mariner 28-30 HP 2-Stroke engines (1980–1988) with serial numbers beginning with 689.
It provides a direct interchange for Yamaha part numbers 689-11631-00-95, 689-11631-00-94, 689-11631-00-96, 689-11631-00-97, 689-11631-00-98; Mariner 7196M, 7197M, 7198M, 761-8484M, 8484M; and Sierra 18-4138.
- Standard Size (STD) bore installation.
- Designed for gasoline (2-Stroke) outboard engines.
- Complete kit includes piston, rings, pin, and clips for a full replacement.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 689-11631-00-95 |
| Yamaha | 689-11631-00-94 |
| Yamaha | 689-11631-00-96 |
| Yamaha | 689-11631-00-97 |
| Yamaha | 689-11631-00-98 |
| Mariner | 7196M / 7197M / 7198M / 761-8484M / 8484M |
| Sierra | 18-4138 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Yamaha, this kit fits select 25 HP and 30 HP 2-stroke outboards from 1984 to 1992.
For Mariner, this kit is compatible with 28 HP and 30 HP 2-stroke engines from 1980 to 1988 having a serial number that starts with 689.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 25ELK | 25 | 2-Stroke | 1985 | 689-11631-00-95 | |
| Yamaha | 25ESK | 25 | 2-Stroke | 1985 | 689-11631-00-95 | |
| Yamaha | 25LK | 25 | 2-Stroke | 1985 | 689-11631-00-95 | |
| Yamaha | 25SK | 25 | 2-Stroke | 1985 | 689-11631-00-95 | |
| Yamaha | 30ELN | 30 | 2-Stroke | 1984 | 689-11631-00-95 | |
| Yamaha | 30ESN | 30 | 2-Stroke | 1984 | 689-11631-00-95 | |
| Yamaha | 30ELK | 30 | 2-Stroke | 1985 | 689-11631-00-95 | |
| Yamaha | 30ESK | 30 | 2-Stroke | 1985 | 689-11631-00-95 | |
| Yamaha | 30ELJ | 30 | 2-Stroke | 1986 | 689-11631-00-95 | |
| Yamaha | 30ESJ | 30 | 2-Stroke | 1986 | 689-11631-00-95 | |
| Yamaha | 30J | 30 | 2-Stroke | 1986 | 689-11631-00-95 | |
| Yamaha | CV30ELF | 30 | 2-Stroke | 1989 | 689-11631-00-95 | |
| Yamaha | CV30ELD | 30 | 2-Stroke | 1990 | 689-11631-00-95 | |
| Yamaha | C30ELRP | 30 | 2-Stroke | 1991 | 689-11631-00-95 | |
| Yamaha | C30ELRQ | 30 | 2-Stroke | 1992 | 689-11631-00-95 | |
| Yamaha | WJ500H | 30 | 2-Stroke | 1987 | 689-11631-00-95 | |
| Yamaha | WR500H | 30 | 2-Stroke | 1987 | 689-11631-00-95 | |
| Yamaha | WJ500G | 30 | 2-Stroke | 1988 | 689-11631-00-95 | |
| Yamaha | WR500H_G | 30 | 2-Stroke | 1988 | 689-11631-00-95 | |
| Mariner | 30HP | 30 | 2-Stroke | 1980–1988 | 761-8484M/8484M | Serial number begins with 689 |
| Mariner | 28HP | 28 | 2-Stroke | 1980–1988 | 761-8484M/8484M |
Technical Specs
- Product Type
- Piston Kit
- Installation
- Standard Size (STD)
- Fuel Type
- Gasoline (2-Stroke)
- Piston Diameter
- 72.00 mm
- Piston Height
- 72.75 mm
- Wrist Pin Diameter
- 20 mm
- Product Weight
- 0.38 kg (0.84 lb)
- Shipping Dimensions
- 3.5" L x 3.13" W x 3.0" H
What’s in the Box
- 1 x Piston (689-11631-00-00)
- 1 x Piston Ring Set (689-11610-00-00)
- 1 x Piston Pin (689-11633-00-00)
- 2 x Piston Pin Clip (688-11634-00-00)
Installation Notes
- Disconnect the battery and fuel lines for safety.
- Remove the engine cover, spark plugs, and cylinder head.
- Carefully push the old piston out of the cylinder bore.
- Thoroughly clean the cylinder and inspect for any scoring or damage. Lightly hone if necessary.
- Lubricate the new piston, rings, and cylinder wall liberally with 2-stroke engine oil.
- Compress the piston rings and gently guide the new piston assembly into the cylinder.
- Reassemble the cylinder head, ensuring bolts are tightened to the manufacturer's specified torque sequence.
- Reconnect all components and prime the fuel system before starting the engine.
Troubleshooting & FAQ
How do I know if this piston kit will fit my specific engine?
The surest way is to match your engine's model and year against the compatibility table. For Mariner models, it is crucial that your engine's serial number begins with "689" as specified.
What are the signs of a worn or failing piston?
Common symptoms include low compression, excessive blue or white smoke from the exhaust, a knocking or rattling sound from the engine, and a noticeable loss of power.
Is this a standard size piston? Will I need to bore my cylinder?
Yes, this is a Standard Size (STD) piston kit. It is designed for cylinders that are within original factory specifications. If your cylinder is worn or damaged, it may need to be bored to an oversize, which would require an oversize piston.
Should I hone the cylinder before installing the new piston?
Yes, it is highly recommended to lightly hone the cylinder bore before installation. This process creates a cross-hatch pattern on the cylinder walls that helps the new piston rings seat properly, ensuring optimal compression and performance.
What is the difference between an OEM and aftermarket piston?
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 facility and are batch-inspected for quality and consistency.
How fast do you ship and what does it cost?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact our support team with your order details. Returns are accepted within our standard window for unused items in their original condition. Please 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 recommended for safety and optimal 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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