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Description
Marine Thermostat – Fits Yamaha F300/F350 4-Stroke V8 Outboards (Replaces 6AW-12411-00-00)Marine Thermostat Fits Yamaha F300 F350 4 Stroke V8 Outboards This marine thermostat is designed for Yamaha 4 Stroke 300HP & 350HP V8 outboards manufactured between 2007 and 2018. It ensures your engine maintains the correct operating temperature for optimal performance and longevity. It serves as a direct replacement for Yamaha part number 6AW 12411 00 00 and Sierra part number 18 3634. Installation Method: Direct OEM style fit Operating Temperature:
Marine Thermostat – Fits Yamaha F300/F350 4-Stroke V8 Outboards
This marine thermostat is designed for Yamaha 4-Stroke 300HP & 350HP V8 outboards manufactured between 2007 and 2018. It ensures your engine maintains the correct operating temperature for optimal performance and longevity.
It serves as a direct replacement for Yamaha part number 6AW-12411-00-00 and Sierra part number 18-3634.
- Installation Method: Direct OEM-style fit
- Operating Temperature: 60°C / 140°F
- Compatible Fuel Type: Gasoline
Part Number Cross-Reference
Use this table to confirm equivalent part numbers across OEM and aftermarket brands.
| Brand | Part Number |
|---|---|
| Yamaha | 6AW-12411-00-00 |
| Sierra | 18-3634 |
Compatible Engine Models
Confirm your engine model/year in the table below. For Yamaha owners, here’s a guide to help you identify your engine’s serial/model: Yamaha Serial Number Guide. You can also review exploded diagrams to verify part numbers: Yamaha Parts Diagrams & Catalog.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Yamaha | F300TUR | 300 | 4-Stroke | 2007–2009 | 6AW-12411-00-00 |
| Yamaha | F300TXR | 300 | 4-Stroke | 2007–2009 | 6AW-12411-00-00 |
| Yamaha | LF300TUR | 300 | 4-Stroke | 2007–2009 | 6AW-12411-00-00 |
| Yamaha | LF300TXR | 300 | 4-Stroke | 2007–2009 | 6AW-12411-00-00 |
| Yamaha | F350TUR | 350 | 4-Stroke | 2007–2009 | 6AW-12411-00-00 |
| Yamaha | F350TXR | 350 | 4-Stroke | 2007–2009 | 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 | F350AET1U | 350 | 4-Stroke | 2010 | 6AW-12411-00-00 |
| Yamaha | F350AET1X | 350 | 4-Stroke | 2010 | 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 | F350UCA | 350 | 4-Stroke | 2010–2011 | 6AW-12411-00-00 |
| Yamaha | F350XCA | 350 | 4-Stroke | 2010–2011 | 6AW-12411-00-00 |
| Yamaha | LF350UCA | 350 | 4-Stroke | 2010–2011 | 6AW-12411-00-00 |
| Yamaha | LF350XCA | 350 | 4-Stroke | 2010–2011 | 6AW-12411-00-00 |
| Yamaha | F350UCB | 350 | 4-Stroke | 2012–2015 | 6AW-12411-00-00 |
| Yamaha | F350XCB | 350 | 4-Stroke | 2012–2015 | 6AW-12411-00-00 |
| Yamaha | LF350UCB | 350 | 4-Stroke | 2012–2015 | 6AW-12411-00-00 |
| Yamaha | LF350XCB | 350 | 4-Stroke | 2012–2015 | 6AW-12411-00-00 |
| Yamaha | F350NCB | 350 | 4-Stroke | 2014–2015 | 6AW-12411-00-00 |
| Yamaha | F350UCC | 350 | 4-Stroke | 2016–2018 | 6AW-12411-00-00 |
| Yamaha | F350XCC | 350 | 4-Stroke | 2016–2018 | 6AW-12411-00-00 |
| Yamaha | F350NCC | 350 | 4-Stroke | 2016 | 6AW-12411-00-00 |
| Yamaha | LF350UCC | 350 | 4-Stroke | 2016–2018 | 6AW-12411-00-00 |
| Yamaha | LF350XCC | 350 | 4-Stroke | 2016–2018 | 6AW-12411-00-00 |
Technical Specifications
| Product Type | Marine Thermostat |
| Installation | Direct OEM Replacement |
| Fuel Type | Gasoline |
| Operating Temperature | 60°C / 140°F |
| Other Technical Attributes | For Yamaha V8 outboard cooling systems |
Package Contents
- 1 × 60°C / 140°F Outboard Thermostat (Replaces OEM Part #6AW-12411-00-00)
Installation Guide
- Safety First: Ensure the engine is completely cool and disconnect the battery before starting.
- Drain Coolant: Place a container under the engine and carefully drain the cooling system to a level below the thermostat housing.
- Locate Housing: Identify the thermostat housing on the engine block. It is typically connected to the main coolant hoses.
- Remove Housing Cover: Loosen and remove the bolts securing the thermostat housing cover. Note the orientation of the cover and gasket.
- Remove Old Thermostat: Carefully lift out the old thermostat and gasket. Clean any sealant residue or corrosion from the housing surfaces.
- Install New Thermostat: Place the new thermostat into the housing, ensuring it is oriented correctly (the spring side usually faces the engine). Install the new gasket.
- Reassemble: Secure the housing cover and tighten the bolts to the manufacturer's recommended torque specification. Do not overtighten.
- Refill and Check: Reconnect hoses if they were removed. Refill the cooling system with the appropriate coolant.
- Final Inspection: Reconnect the battery. Start the engine and let it warm up, carefully checking for any leaks around the thermostat housing. Top off coolant if necessary.
Troubleshooting & FAQ
Q: How do I confirm this thermostat fits my engine?
A: First, check the 'Compatible Engine Models' table on this page to ensure your specific engine model and year range are listed. Second, cross-reference the OEM part number 6AW-12411-00-00 with the part number specified in your engine’s service manual.
Q: What are the common signs of a failing thermostat?
A: Key symptoms include engine overheating alarms, the temperature gauge reading higher or lower than normal, or the engine taking an unusually long time to reach its standard operating temperature. A thermostat stuck open can cause the engine to run too cool, while one stuck closed will lead to overheating.
Q: How often should I replace my outboard's thermostat?
A: As a preventative maintenance measure, we recommend inspecting your thermostat annually and replacing it every 2-3 years, or according to the service interval in your owner's manual. Replacement is especially important for engines used in saltwater environments, where corrosion can cause parts to fail prematurely.
Q: OEM vs. Aftermarket?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.
Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.
Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.
Important Notes
- Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
- This product is an aftermarket replacement part and is not an OEM component.
- Professional installation is recommended to ensure safety and optimal performance.
Why Choose JLM MARINE?
- Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
- Fast Global Shipping: Free delivery worldwide in 5–15 days.
- Direct from Manufacturer: Competitive pricing without compromising quality.
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy