Marine Thermostat – Fits Yamaha F300/F350 4-Stroke V8 Outboards (Replaces 6AW-12411-00-00)

Vendor: JLM Marine
Availability: In Stock
Product Type: Thermostat
$23.00
$23.00
Subtotal: $23.00

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Marine Thermostat – Fits Yamaha F300/F350 4 - Stroke V8 Outboards (Replaces 6AW - 12411 - 00 - 00) - JLM Marine Boat Parts Limited

Marine Thermostat – Fits Yamaha F300/F350 4-Stroke V8 Outboards (Replaces 6AW-12411-00-00)

$23.00

Marine Thermostat – Fits Yamaha F300/F350 4-Stroke V8 Outboards (Replaces 6AW-12411-00-00)

$23.00

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: 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

  1. Safety First: Ensure the engine is completely cool and disconnect the battery before starting.
  2. Drain Coolant: Place a container under the engine and carefully drain the cooling system to a level below the thermostat housing.
  3. Locate Housing: Identify the thermostat housing on the engine block. It is typically connected to the main coolant hoses.
  4. Remove Housing Cover: Loosen and remove the bolts securing the thermostat housing cover. Note the orientation of the cover and gasket.
  5. Remove Old Thermostat: Carefully lift out the old thermostat and gasket. Clean any sealant residue or corrosion from the housing surfaces.
  6. 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.
  7. Reassemble: Secure the housing cover and tighten the bolts to the manufacturer's recommended torque specification. Do not overtighten.
  8. Refill and Check: Reconnect hoses if they were removed. Refill the cooling system with the appropriate coolant.
  9. 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.

We can ship to virtually any address in the world with free shipping available for most regions.

For our typical US and Canadian customers , our shipping timeframes are as follows:

  • Amazon FBA: orders will be delivered within 1-5 business days after placing the order (during certain special periods such as major promotions, Christmas, etc., the delivery time of Amazon FBA may be affected).
  • US warehouse shipment: orders will be delivered within 5 days after placing the order.
  • China warehouse shipment: orders will be delivered about 12 days after placing the order.

When you place an order, we will estimate shipping and delivery dates for you based on the availability of your items and the shipping options you choose. Depending on the shipping provider you choose, shipping date estimates may appear on the shipping quotes page.

Please also note that the shipping rates for many items we sell are weight-based. The weight of any such item can be found on its detail page. To reflect the policies of the shipping companies we use, all weights will be rounded up to the next full pound.

Founded in 2002, JLM Marine has established itself as a dedicated manufacturer of high-quality marine parts, based in China. Our commitment to excellence in manufacturing has earned us the trust of top marine brands globally.

As a direct supplier, we bypass intermediaries, which allows us to offer competitive prices without compromising on quality. This approach not only supports cost-efficiency but also ensures that our customers receive the best value directly from the source.

We are excited to expand our reach through retail channels, bringing our expertise and commitment to quality directly to boat owners and enthusiasts worldwide.

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