Lower Base Gasket – Fits Yamaha 40HP 2-Stroke Outboard Motors (Replaces 66T-45114-A0)
Lower Base Gasket – Fits Yamaha 40HP 2-Stroke Outboard Motors (Replaces 66T-45114-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).
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 Lower Base Gasket – Fits Yamaha 40HP 2-Stroke Outboard Motors (Replaces 66T-45114-A0) creates a critical seal between the lower base and engine block. It is designed for Yamaha 40HP 2-stroke engines (including models E40X, 40XMH, E40XMH, 40XW, and 40XWT) from years 1998–2014, preventing fluid leaks and maintaining optimal performance.
This part serves as a direct replacement for Yamaha OEM part number 66T-45114-A0.
- Installation Method: Direct replacement
- Material: High-quality paper/composite gasket material for a durable seal
- Function: Essential for preventing oil and coolant leaks between major engine components
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 66T-45114-A0 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 40X | 40 | 2-Stroke | 1998–2001 | 66T-45114-A0 | |
| Yamaha | 40XMH | 40 | 2-Stroke | 2003–2014 | 66T-45114-A0 | |
| Yamaha | 40XW | 40 | 2-Stroke | 2006–2014 | 66T-45114-A0 | |
| Yamaha | 40XWH | 40 | 2-Stroke | 2006 | 66T-45114-A0 | |
| Yamaha | 40XWT | 40 | 2-Stroke | 2006 | 66T-45114-A0 | |
| Yamaha | E40MLH | 40 | 2-Stroke | 1998–2000 | 66T-45114-A0 | |
| Yamaha | E40X | 40 | 2-Stroke | 1998–2001 | 66T-45114-A0 |
Technical Specs
- Product Type
- Lower Base Gasket
- Installation
- Direct replacement
- Fuel Type
- Gasoline (2-stroke)
- Material
- Paper/composite gasket material
- Product Dimensions
- 31.0 cm (L) x 21.0 cm (H) x 0.2 cm (W)
- Warranty
- 1 year (TMP Global warranty)
- OEM Part Number
- 66T-45114-A0
- Other Technical Attributes
- Essential for maintaining a tight seal between the lower base and the engine block
What’s in the Box
- 1 x Lower Base Gasket (66T-45114-A0)
Installation Notes
- Ensure the engine is off, cool, and disconnected from the power source.
- Drain engine oil or other fluids as necessary to avoid spills.
- Carefully remove any components obstructing access to the lower engine base.
- Remove the old gasket and meticulously clean both mating surfaces. Any remaining debris can cause leaks.
- Position the new gasket correctly. Ensure all bolt holes align perfectly.
- Reassemble the components, tightening bolts in the sequence and to the torque values specified by the manufacturer.
- Refill any drained fluids, reconnect the battery, and run the engine while carefully checking for any signs of leaks.
Troubleshooting & FAQ
How do I know if my lower base gasket is failing?
Common signs include visible fluid leaks (oil or coolant) around the engine block's base, engine overheating, or an unexplained loss of performance. A physical inspection will often reveal gasket degradation or breaches.
Is this gasket a direct fit for my Yamaha 40XMH engine?
Yes, this gasket is engineered as a direct replacement for the specified Yamaha 40HP 2-stroke models, including the 40XMH (2003–2014). To guarantee fitment, always verify your engine's OEM part number requirement is 66T-45114-A0.
When should this gasket be replaced?
Gaskets do not have a fixed service interval. They should be replaced any time the parts they seal are disassembled for service or if you observe any signs of a leak.
What is the main difference between this and an original Yamaha gasket?
This is a high-quality aftermarket part designed to meet or exceed OEM specifications for material, fit, and function. It provides a reliable, leak-free seal comparable to the original at a better value.
Is this an OEM part?
This listing is for an aftermarket replacement, not an OEM component. It is built to OEM-level specifications with comparable materials and manufactured in an ISO 9002 facility, with batch inspections for consistency.
How fast is shipping?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free, with expedited options available at checkout where applicable.
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 unused items in their original condition.
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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