Upper Casing Gasket – Fits Yamaha 40HP 2-Stroke Outboards (Replaces 66T-45113-A0)
Upper Casing Gasket – Fits Yamaha 40HP 2-Stroke Outboards (Replaces 66T-45113-A0) 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 replacement Upper Casing Gasket provides a precise seal for the engine block on various Yamaha 40HP 2-stroke outboard engines produced between 1998 and 2017, including models E40X, 40X, and 40XMH series.
It serves as a direct interchange for Yamaha OEM part numbers 66T-45113-A0 and 66T-45113-A0-00.
- Installs between the engine block and upper casing.
- Designed for 2-stroke gasoline outboard engines.
- Engineered from a durable paper/composite material for a reliable seal.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 66T-45113-A0 |
| Yamaha | 66T-45113-A0-00 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This part is compatible with select Yamaha 40HP 2-stroke outboards. Please verify your specific model and year before ordering.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 40X | 40 | 2-Stroke | 1998–2012 | 66T-45113-A0 | M(W/T)HS/L variants |
| Yamaha | E40X | 40 | 2-Stroke | 1998–1999 | 66T-45113-A0 | M(W/T)HS/L variants |
| Yamaha | E40X | 40 | 2-Stroke | 2001–2008 | 66T-45113-A0 | M(W/T)HS/L variants |
| Yamaha | E40X | 40 | 2-Stroke | 2010–2017 | 66T-45113-A0 | MHL variant |
| Yamaha | E40X | 40 | 2-Stroke | 2010 | 66T-45113-A0 | MHS variant |
Technical Specs
- Product Type
- Upper Casing Gasket
- Installation
- Engine Block, Upper Casing
- Fuel Type
- Gasoline
- Housing Material
- Paper/Composite Material
- Housing Color
- Gray
- Dimensions
- 31.0cm x 21.0cm x 0.4cm
- Weight
- 0.100kg (0.22 lb)
- Engine Type
- 2-Stroke
What’s in the Box
- 1 x Upper Casing Gasket (66T-45113-A0)
Installation Notes
- Ensure the engine is off, cool, and disconnected from the battery.
- Drain any fluids as required by your service manual to prevent spills.
- Remove components necessary to access the upper casing interface.
- Carefully take off the old gasket and thoroughly clean all metal mating surfaces of any residue.
- Verify the surfaces are clean, dry, and free of damage.
- Position the new gasket. Do not use sealant unless explicitly recommended by the manufacturer's service manual.
- Reassemble all components, torquing bolts to the specified values and in the correct sequence.
- Refill any drained fluids, reconnect the battery, and inspect for leaks after starting the engine.
Troubleshooting & FAQ
How do I know if this gasket will fit my Yamaha 40HP outboard?
This gasket is designed for specific Yamaha 40HP 2-stroke models listed in the compatibility table, including series like 40X and E40X from 1998–2017. Always cross-reference your engine's model and serial number against the chart and confirm the OEM part number is 66T-45113-A0.
What are the signs of a failed upper casing gasket?
Common signs of a bad gasket include visible water or oil leaks around the upper casing seam, engine overheating, loss of compression, or water contamination in the engine oil. If you notice these symptoms, inspect the area immediately.
Should I use sealant when installing this gasket?
Generally, this type of gasket is designed to be installed dry. Unless your official service manual specifies the use of a sealant for your particular engine model, do not apply any. Using sealant where none is required can cause improper sealing or block fluid passages.
How often should this gasket be replaced?
This gasket does not have a set replacement interval. It should be replaced whenever the upper casing is removed for service, or if you detect signs of a leak or failure.
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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