Cylinder Head Gasket – Fits Yamaha 40HP 2-Stroke Outboards (Replaces 66T-11181-A2)
Cylinder Head Gasket – Fits Yamaha 40HP 2-Stroke Outboards (Replaces 66T-11181-A2) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Cylinder Head Gasket – Fits Yamaha 40HP 2-Stroke Outboards (Replace...
Product Details
This aftermarket Cylinder Head Gasket – Fits Yamaha 40HP 2-Stroke Outboards (Replaces 66T-11181-A2) is engineered for Yamaha's 40HP, 40X, and E40X 2-stroke models from 1998 and later. It creates a critical seal between the cylinder head and the engine block, preventing combustion gas leakage and the mixing of oil and coolant.
It serves as a direct interchange for Yamaha part numbers 66T-11181-00, 66T-11181-A0, 66T-11181-A2, 66T-11181-A3, 66T-11181-03-00, and Parsun T40-05000002.
- Installation: Designed as a direct replacement component for a seamless fit.
- Material: Constructed from durable multi-layered metal with molded rubber seals for a long-lasting, reliable seal.
- Engine Type: Specifically for 2-stroke gasoline outboard engines.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number | Notes |
|---|---|---|
| Yamaha | 66T-11181-A2 | Primary replacement number |
| Yamaha | 66T-11181-00 | Interchangeable predecessor |
| Yamaha | 66T-11181-A0 | Interchangeable predecessor |
| Yamaha | 66T-11181-A3 | Interchangeable part |
| Yamaha | 66T-11181-03-00 | Interchangeable part |
| Parsun | T40-05000002 | Aftermarket cross-reference |
Engine & Model Compatibility
Confirm your engine model and year in the table below to ensure correct fitment.
For Yamaha Owners: This part fits various Yamaha 40HP 2-stroke models manufactured in 1998 and later. Please verify your specific model designation (e.g., 40XMH, E40XW).
For Parsun Owners: This part is known to be compatible with Parsun T40 40HP 2-Stroke models that are based on the Yamaha engine design.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Yamaha | E40X | 40 | 2-Stroke | 1998 and later | 66T-11181-A2 |
| Yamaha | 40X | 40 | 2-Stroke | 1998 and later | 66T-11181-A2 |
| Yamaha | 40XMH | 40 | 2-Stroke | 1998 and later | 66T-11181-A2 |
| Yamaha | E40XMH | 40 | 2-Stroke | 1998 and later | 66T-11181-A2 |
| Yamaha | E40XW | 40 | 2-Stroke | 1998 and later | 66T-11181-A2 |
| Yamaha | E40XWT | 40 | 2-Stroke | 1998 and later | 66T-11181-A2 |
Technical Specs
- Product Type
- Cylinder Head Gasket
- Installation
- Direct replacement
- Fuel Type
- Gasoline (2-stroke)
- Housing Material
- Multi-layered metal with molded rubber
- Dimensions
- 26.0 cm L x 15.0 cm W x 0.5 cm H
- Warranty
- 1 Year
What’s in the Box
- 1 x Cylinder Head Gasket (Replaces 66T-11181-A2 / 66T-11181-00)
Installation Notes
- Disconnect the battery and relieve any fuel system pressure.
- Drain the engine coolant completely.
- Remove any components obstructing access to the cylinder head.
- Loosen and remove the cylinder head bolts in the reverse order of the manufacturer's tightening sequence.
- Carefully lift the cylinder head off the engine block. Avoid using pry tools that could damage the mating surfaces.
- Remove the old head gasket. Thoroughly clean both the cylinder head and engine block surfaces of any old gasket material, oil, or debris.
- Position the new gasket correctly onto the engine block dowels. No sealants should be used unless explicitly required by your service manual.
- Carefully lower the cylinder head back into place.
- Lightly oil the threads of the cylinder head bolts and install them finger-tight.
- Using a calibrated torque wrench, tighten the bolts in multiple stages, following the specific sequence and torque values in your engine's service manual.
- Reinstall all previously removed components.
- Refill the cooling system, reconnect the battery, and start the engine, checking carefully for any leaks.
Troubleshooting & FAQ
How do I confirm this gasket fits my specific Yamaha 40HP model?
Check the "Engine & Model Compatibility" table on this page. Your engine model (e.g., E40X, 40XMH) and year must be listed. Always cross-reference the OEM part number (66T-11181-A2 or its equivalents) with your service manual for 100% certainty.
What are common symptoms of a failing cylinder head gasket?
The most common signs include engine overheating, a noticeable loss of power, white steam/smoke from the exhaust, milky or foamy engine oil, and external oil or coolant leaks from the seam between the cylinder head and engine block.
Is this a multi-layered steel (MLS) gasket?
Yes, this gasket is constructed from multiple layers of embossed steel with molded rubber seals. This design provides superior durability and sealing capability compared to older composite gaskets.
Should I use sealant or gasket adhesive during installation?
No. This type of gasket is designed to be installed completely dry. The integrated rubber seals provide all the necessary sealing. Applying additional sealants can interfere with its performance, compromise the seal, and may lead to premature failure.
What causes a cylinder head gasket to fail?
The primary cause of failure is engine overheating, which can cause the cylinder head to warp and compromise the seal. Other causes include improper installation (incorrect bolt torque), engine detonation (knocking), or simply material fatigue from age and hours of use.
Is there a break-in period after replacing a head gasket?
While no formal break-in is required, it is wise to run the engine at varying, moderate speeds for the first hour of operation. Avoid full-throttle acceleration during this time. Allow the engine to cool down completely, then re-check the torque of the head bolts if recommended by your service manual.
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 and specifications against your original part before purchasing. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement component, not an Original Equipment Manufacturer (OEM) part.
- Professional installation is strongly recommended for safety, proper function, and engine longevity.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions, typically arriving in 5–15 days.
- Manufacturer-Direct Value — By removing middlemen, we offer fair pricing without compromising on materials or quality control.
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