Cylinder Head Gasket – Fits Yamaha 25-30 HP 3-Cylinder Outboards (Replaces 6J8-11181-A2-00)
Cylinder Head Gasket – Fits Yamaha 25-30 HP 3-Cylinder Outboards (Replaces 6J8-11181-A2-00) 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
Free standard shipping on all orders under 1 KG
Cylinder Head Gasket – Fits Yamaha 25-30 HP 3-Cylinder Outboards (R...
Product Details
This replacement Cylinder Head Gasket is designed to fit a wide range of Yamaha 25-30 HP 3-cylinder, 2-stroke outboard motors manufactured between 1986 and 2009, including the popular 25J and 30D series engines. It provides a reliable seal for the engine's powerhead assembly.
This part serves as a direct replacement for Yamaha OEM part numbers 6J8-11181-A2-00, 6J8-11181-A1-00, 6J8-11181-A0-00, and 6J8-11181-00-00, and interchanges with Sierra 18-3829 and GLM 34920.
- Installation Location: Engine Powerhead
- Material: High-performance composite and metal construction
- Primary Function: Seals the cylinder head to the engine block
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number | Notes |
|---|---|---|
| Yamaha | 6J8-11181-A2-00 | Current OEM Part Number |
| Yamaha | 6J8-11181-A1-00 | Superseded by 6J8-11181-A2-00 |
| Yamaha | 6J8-11181-A0-00 | Superseded by 6J8-11181-A1-00 |
| Yamaha | 6J8-11181-00-00 | Superseded by 6J8-11181-A0-00 |
| Sierra | 18-3829 | Aftermarket Interchange |
| GLM | 34920 | Aftermarket Interchange |
Engine & Model Compatibility
Confirm your engine model and year in the table below. This part is designed for specific 3-cylinder Yamaha outboards.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 25J | 25 | 2-Stroke | 1987–2005 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 25JEO | 25 | 2-Stroke | 1992–1994, 1997 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 25JETO | 25 | 2-Stroke | 1998 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 25ESH | 25 | 2-Stroke | 1999 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 25MSHZ | 25 | 2-Stroke | 2001 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30D | 30 | 2-Stroke | 1986–2009 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30DM | 30 | 2-Stroke | 1993–1998 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30DMHO | 30 | 2-Stroke | 1998 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30DE | 30 | 2-Stroke | 1999 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30DETO | 30 | 2-Stroke | 1999 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30DMH | 30 | 2-Stroke | 1999 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30DWH | 30 | 2-Stroke | 1999 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30ELH | 30 | 2-Stroke | 1999 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30DEL | 30 | 2-Stroke | 2001 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30DETOL | 30 | 2-Stroke | 2001–2002 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30DMHL | 30 | 2-Stroke | 2001 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30DWHL | 30 | 2-Stroke | 2001 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30ELA | 30 | 2-Stroke | 2001 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30ERZ | 30 | 2-Stroke | 2001 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30MHZ | 30 | 2-Stroke | 2001 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | 30MSHA | 30 | 2-Stroke | 2002 | 6J8-11181-A2-00 | 3-cylinder models |
| Yamaha | Various 30HP suffix variants | 30 | 2-Stroke | 2003–2009 | 6J8-11181-A2-00 | Multiple model suffixes through 2009 |
Technical Specs
- Product Type
- Cylinder Head Gasket
- Installation
- Engine Powerhead
- Material
- Composite/Metal
- Engine Compatibility
- 3-Cylinder Outboard
- Compatible Engine Series
- 25J, 30D
- Engine Type
- 2-Stroke
- Reference OEM Part Number
- 6J8-11181-A2-00
- Product Dimensions
- 31.0 cm L x 21.0 cm W x 0.5 cm H
What’s in the Box
- 1 x Cylinder Head Gasket (Replaces 6J8-11181-A2-00)
Installation Notes
- Disconnect the negative battery cable and drain the engine's cooling system completely.
- Carefully remove any components obstructing access to the cylinder head, such as the flywheel cover or ignition coils.
- Loosen and remove the cylinder head bolts in the reverse order of the tightening sequence specified in your service manual.
- Gently lift the cylinder head off the block. If it's stuck, do not pry between the mating surfaces; tap it with a soft mallet.
- Remove the old head gasket. Thoroughly clean both the cylinder head and engine block surfaces of all old gasket material and debris.
- Position the new gasket correctly on the engine block; ensure it is not installed upside down or backward.
- Carefully place the cylinder head back onto the block, ensuring it is aligned with the dowels.
- Install and tighten the head bolts in the sequence and to the torque values specified by the manufacturer. This is critical for a proper seal.
- Reinstall all components removed earlier, refill the cooling system, and reconnect the battery.
- Start the engine and let it warm up, checking carefully for any coolant or exhaust leaks around the cylinder head.
Troubleshooting & FAQ
How do I confirm this gasket is the right one for my Yamaha outboard?
Verify your engine's model, horsepower, and year against the "Engine & Model Compatibility" table. This gasket is specifically for Yamaha 25 HP and 30 HP 3-cylinder, 2-stroke outboards in the 25J and 30D series. Cross-referencing your old part number with our "Part Number Matrix" is also a reliable way to confirm fitment.
Should I use a sealant or adhesive with this head gasket?
This gasket is designed to be installed dry. Applying sealants can interfere with its ability to create a proper seal and may cause premature failure. Always clean both mating surfaces thoroughly before installation and refer to your engine's official service manual for any model-specific directives.
What are the typical symptoms of a blown head gasket on an outboard?
Signs of a failed head gasket include engine overheating, a noticeable loss of power or compression, water-contaminated (milky) oil, excessive white smoke from the exhaust (steam), or visible water leaks from the cylinder head joint.
What can cause a new head gasket to fail?
The most common causes are improper installation, such as failing to clean the mating surfaces, incorrect torque values, or an incorrect tightening sequence on the head bolts. Engine overheating can also compromise a new gasket. Always follow the manufacturer's service manual.
Is this a genuine Yamaha (OEM) part?
This listing is an aftermarket replacement, not an OEM component. It is engineered to meet or exceed OEM-level specifications using comparable materials. Our parts are manufactured in an ISO 9001 certified facility and are batch-inspected to ensure quality and consistency.
How fast do you ship?
We ship worldwide quickly—typical transit is 5–15 days for most destinations. Standard shipping is free. If available for your location, expedited shipping options and costs will be presented at checkout.
What is the warranty and return policy?
This part is covered by a 1-year warranty against manufacturing defects under normal marine use. If you encounter an issue, please contact our support team with your order details. Returns are accepted within our standard window_ for unused items in their original packaging. Please see our full policy page or contact us for instructions.
Safety & Important Info
- Verify the product images and specifications against your original part before purchase. If anything differs—even if your model is listed as compatible—do not install the part and contact us for clarification.
- This is a high-quality aftermarket replacement component, not an original equipment manufacturer (OEM) product.
- Professional installation by a qualified marine mechanic is strongly recommended to ensure safety, proper performance, and engine longevity.
About Sea Sierra
- Pro-Grade Standards: We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world reliability in harsh marine environments.
- Fast Global Fulfillment: We offer free standard delivery to most regions with an average transit time of 5–15 days, getting you back on the water sooner.
- Manufacturer-Direct Value: By working directly with our manufacturing partners, we provide fair pricing without ever compromising on materials or quality control.
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