Thermostat – Fits Yamaha 300-350HP 4-Stroke Outboard (Replaces 6AW-12411-00-00)
Thermostat – Fits Yamaha 300-350HP 4-Stroke Outboard (Replaces 6AW-12411-00-00) 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
Product Details
This replacement Thermostat fits Yamaha 300-350HP 4-Stroke Outboard engines, specifically V8 models manufactured from 2007 through 2017. It is a critical component designed to regulate your engine's cooling system for optimal performance and longevity.
It serves as a direct interchange for OEM part number 6AW-12411-00-00 and aftermarket references including Sierra 18-3634 and EMP 6AW-12411-00-00.
- Engineered for direct OEM replacement fit and function.
- Essential for regulating the engine's operating temperature.
- Backed by a 12-month manufacturer warranty for peace of mind.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket suppliers.
| Brand | Part Number |
|---|---|
| Yamaha | 6AW-12411-00-00 |
| Sierra | 18-3634 |
| EMP | 6AW-12411-00-00 |
| WATERLONG | 6AW-12411-00-00 |
Engine & Model Compatibility
Confirm your engine model and year in the table below to ensure accurate fitment.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | F300TUR | 300 | 4-Stroke | 2007–2008 | 6AW-12411-00-00 | |
| Yamaha | F300TUR | 300 | 4-Stroke | 2009 | 6AW-12411-00-00 | |
| Yamaha | F300TUR | 300 | 4-Stroke | 2007–2012 | 6AW-12411-00-00 | |
| Yamaha | F300TXR | 300 | 4-Stroke | 2007–2008 | 6AW-12411-00-00 | |
| Yamaha | F300TXR | 300 | 4-Stroke | 2009 | 6AW-12411-00-00 | |
| Yamaha | F300TXR | 300 | 4-Stroke | 2007–2012 | 6AW-12411-00-00 | |
| Yamaha | F350AET1U | 350 | 4-Stroke | 2010 | 6AW-12411-00-00 | |
| Yamaha | F350AET1X | 350 | 4-Stroke | 2010 | 6AW-12411-00-00 | |
| Yamaha | F350NCB | 350 | 4-Stroke | 2014–2015 | 6AW-12411-00-00 | |
| Yamaha | F350NCC | 350 | 4-Stroke | 2016 | 6AW-12411-00-00 | |
| Yamaha | F350TUR | 350 | 4-Stroke | 2007 | 6AW-12411-00-00 | |
| Yamaha | F350TUR | 350 | 4-Stroke | 2008–2009 | 6AW-12411-00-00 | |
| Yamaha | F350TXR | 350 | 4-Stroke | 2007–2009 | 6AW-12411-00-00 | |
| Yamaha | F350UCA | 350 | 4-Stroke | 2010–2011 | 6AW-12411-00-00 | |
| Yamaha | F350UCB | 350 | 4-Stroke | 2012–2015 | 6AW-12411-00-00 | |
| Yamaha | F350UCC | 350 | 4-Stroke | 2016 | 6AW-12411-00-00 | |
| Yamaha | F350XCA | 350 | 4-Stroke | 2010–2011 | 6AW-12411-00-00 | |
| Yamaha | F350XCB | 350 | 4-Stroke | 2012–2015 | 6AW-12411-00-00 | |
| Yamaha | F350XCC | 350 | 4-Stroke | 2016 | 6AW-12411-00-00 | |
| Yamaha | FL350AET1U | 350 | 4-Stroke | 2010 | 6AW-12411-00-00 | |
| Yamaha | FL350AET1X | 350 | 4-Stroke | 2010 | 6AW-12411-00-00 | |
| Yamaha | LF300TUR | 300 | 4-Stroke | 2007–2009 | 6AW-12411-00-00 | |
| Yamaha | LF300TUR | 300 | 4-Stroke | 2007–2012 | 6AW-12411-00-00 | |
| Yamaha | LF300TXR | 300 | 4-Stroke | 2007–2009 | 6AW-12411-00-00 | |
| Yamaha | LF300TXR | 300 | 4-Stroke | 2007–2012 | 6AW-12411-00-00 | |
| Yamaha | LF350TUR | 350 | 4-Stroke | 2007–2009 | 6AW-12411-00-00 | |
| Yamaha | LF350TXR | 350 | 4-Stroke | 2007–2009 | 6AW-12411-00-00 | |
| Yamaha | LF350UCA | 350 | 4-Stroke | 2010–2011 | 6AW-12411-00-00 | |
| Yamaha | LF350UCB | 350 | 4-Stroke | 2012–2015 | 6AW-12411-00-00 | |
| Yamaha | LF350UCC | 350 | 4-Stroke | 2016 | 6AW-12411-00-00 | |
| Yamaha | LF350XCA | 350 | 4-Stroke | 2010–2011 | 6AW-12411-00-00 | |
| Yamaha | LF350XCB | 350 | 4-Stroke | 2012–2015 | 6AW-12411-00-00 | |
| Yamaha | LF350XCC | 350 | 4-Stroke | 2016 | 6AW-12411-00-00 |
Technical Specs
- Product Type
- Thermostat
- Installation
- Direct OEM replacement
- Fuel Type
- Gasoline
- Housing Material
- Metal
- Housing Color
- Silver/Metallic
- Dimensions
- Height: 6.0 in; Width: 6.0 in; Length: 6.0 in;
- Function
- For cooling system regulation
- Warranty
- 12-month warranty (WATERLONG)
What’s in the Box
- 1 x Thermostat (6AW-12411-00-00)
Installation Notes
- Ensure the engine is completely cool before beginning work. Disconnect the battery for safety.
- Locate the thermostat housing on the engine block. Place a drain pan underneath to catch any residual coolant.
- Carefully remove the bolts securing the housing cover. Note their placement and length if they differ.
- Gently pry the housing cover off. If it's stuck, tap it lightly with a rubber mallet. Do not use a screwdriver, as this can damage the sealing surfaces.
- Remove the old thermostat and any gasket or o-ring remnants. Clean both the housing and cover surfaces thoroughly.
- Install the new thermostat, ensuring it is oriented correctly. Place the new gasket or o-ring into position.
- Re-secure the housing cover, tightening the bolts in a crisscross pattern to the manufacturer's specified torque.
- Refill the cooling system, reconnect the battery, and run the engine while checking for leaks and proper temperature gauge operation.
Troubleshooting & FAQ
What are the signs of a failing thermostat?
Common symptoms include the engine overheating at various speeds, or conversely, the engine failing to reach its normal operating temperature, which can lead to poor performance and fuel efficiency.
How can I confirm this part fits my engine?
The most reliable method is to match the OEM part number stamped on your existing thermostat to 6AW-12411-00-00. Additionally, verify your engine model and year against the detailed compatibility list provided on this page.
When should a thermostat be replaced?
Thermostats should be inspected during routine cooling system service and are typically replaced every 2-3 years as preventative maintenance. Replace it immediately if you diagnose any cooling system regulation issues.
Will I need anything else for installation?
This listing includes the thermostat only. A new gasket or o-ring is almost always recommended during replacement to ensure a proper seal. Please check if your service manual requires one and purchase it separately if needed.
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.
Payment & Security
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