Cylinder Head Gasket – Fits Yamaha 40-50HP 3-Cylinder 2-Stroke Outboards (Replaces 6H4-11181-A2-00)
Cylinder Head Gasket – Fits Yamaha 40-50HP 3-Cylinder 2-Stroke Outboards (Replaces 6H4-11181-A2-00) 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
Cylinder Head Gasket – Fits Yamaha 40-50HP 3-Cylinder 2-Stroke Outb...
Product Details
This replacement Cylinder Head Gasket – Fits Yamaha 40-50HP 3-Cylinder 2-Stroke Outboards (Replaces 6H4-11181-A2-00) is engineered to meet or exceed OEM specifications. It is designed for a precise fit on Yamaha 3-cylinder 40HP and 50HP 2-stroke outboard motors, including Pro and P models, manufactured between 1984–1994.
This part provides a direct interchange for Sierra 18-3830, Mallory 9-63953, and Yamaha part numbers 6H4-11181-00-00, 6H4-11181-A0-00, 6H4-11181-A1-00, and 6H4-11181-A2-00.
- Direct replacement part for a seamless installation.
- Seals the cylinder head to the engine block to prevent leaks.
- Constructed from high-quality, OEM-equivalent materials for durability.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket brands.
| Brand | Part Number | Superseded By | Notes |
|---|---|---|---|
| Yamaha | 6H4-11181-00-00 | 6H4-11181-A0-00 | Original OEM part. |
| Yamaha | 6H4-11181-A0-00 | 6H4-11181-A1-00 | OEM supersession. |
| Yamaha | 6H4-11181-A1-00 | 6H4-11181-A2-00 | OEM supersession. |
| Yamaha | 6H4-11181-A2-00 | Current OEM part number. | |
| Sierra | 18-3830 | Aftermarket equivalent. | |
| Mallory | 9-63953 | Aftermarket equivalent. |
Engine & Model Compatibility
Confirm your engine model and year in the table below to ensure correct fitment.
This gasket is designed for select Yamaha 3-cylinder outboards.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 40HP | 40 | 2-Stroke | 1984–1994 | 6H4-11181-A2-00 | 3-cylinder models |
| Yamaha | Pro 50 | 50 | 2-Stroke | 1984–1994 | 6H4-11181-A2-00 | 3-cylinder models |
| Yamaha | P50 | 50 | 2-Stroke | 1984–1994 | 6H4-11181-A2-00 | 3-cylinder models |
| Yamaha | 50HP | 50 | 2-Stroke | 1984–1994 | 6H4-11181-A2-00 | 3-cylinder models |
Technical Specs
- Product Type
- Cylinder Head Gasket
- Installation
- Replacement Part
- Housing Material
- OEM-Equivalent Material
- Dimensions
- 17.5 in × 7.0 in × 0.13 in (L × W × H)
- Function
- Replaces OEM gasket between cylinder head and block
- Warranty
- 1 Year
What’s in the Box
- 1 x Cylinder Head Gasket (Replaces 6H4-11181-A2-00)
Installation Notes
Follow your engine’s official service manual for detailed procedures. These are general, non-comprehensive steps:
- Disconnect the battery and drain the engine's cooling system completely.
- Remove intake/exhaust manifolds, carburetor/fuel rails, and any other components blocking access to the cylinder head.
- Loosen the cylinder head bolts in several passes, following the reverse of the torque sequence specified in your service manual.
- Carefully lift the cylinder head off the engine block. Do not pry between the mating surfaces.
- Remove the old head gasket. Thoroughly clean both the engine block and cylinder head surfaces, ensuring they are free of old gasket material, sealant, oil, and debris.
- Verify the new gasket is correct and place it onto the engine block, ensuring proper alignment with dowel pins. Do not use sealant unless specifically required by the manufacturer.
- Carefully lower the cylinder head back into position on the block.
- Install and tighten the head bolts in the correct sequence and to the torque specifications provided in your service manual. This is critical to ensure a proper seal.
- Reinstall all previously removed components and reconnect all hoses and electrical connectors.
- Refill the cooling system, reconnect the battery, and check for leaks before resuming normal operation.
Troubleshooting & FAQ
How do I know if my cylinder head gasket is failing?
Common signs of a blown head gasket include engine overheating, white smoke from the exhaust (coolant burning), a milky appearance in the engine oil (oil and coolant mixing), loss of compression, or bubbling in the coolant reservoir.
Does this gasket fit all Yamaha 40HP engines?
No. This gasket is specifically for 3-cylinder 40HP and 50HP 2-stroke models made between 1984–1994. Always verify your engine's model and year range using our compatibility table before ordering.
Do I need to use gasket sealant or adhesive during installation?
Generally, modern head gaskets like this one are designed to be installed dry. Applying sealant can interfere with the seal and may cause premature failure. Always follow the specific instructions in your engine’s service manual.
What causes a head gasket to fail?
The most common cause of head gasket failure is engine overheating. Other causes include improper installation (incorrect torque sequence), detonation (engine knock), or simple age and material fatigue over time.
Is this a multi-layer steel (MLS) gasket?
This gasket is manufactured from high-quality, OEM-equivalent materials designed to provide a reliable seal for its specified applications. While the exact material composition can vary, it is engineered for compatibility with the stock engine block and cylinder head surfaces.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials. All parts are manufactured in an ISO 9002 facility and are batch-inspected for quality and consistency.
What are your shipping speed & cost?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free to most regions, and expedited options will appear at checkout if they are available for your location.
What is the warranty and return policy?
This part is covered by a 1-year warranty against manufacturing defects under normal use. If you encounter an issue, please contact our support team with your order details. Returns are accepted within our standard window for items that are unused and in their 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.
Payment & Security
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