Thermostat (140°F/60°C) – Fits Yamaha 20-25HP (Replaces Yamaha 6FM-12411-00-00, AM6FM-12411-00)
Thermostat (140°F/60°C) – Fits Yamaha 20-25HP (Replaces Yamaha 6FM-12411-00-00, AM6FM-12411-00) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
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Thermostat (140°F/60°C) – Fits Yamaha 20-25HP (Replaces Yamaha 6FM-...
Thermostat (140°F/60°C) – Fits Yamaha 20-25HP (Replaces Yamaha 6FM-12411-00-00, AM6FM-12411-00) is backordered and will ship as soon as it is back in stock.
Product Details
This replacement Thermostat (140°F/60°C) is engineered to regulate engine temperature for select Yamaha 4-Stroke outboards. It is specifically compatible with 20HP (F20) models from 2018–2022 and 25HP (F25) models from 2016–2022, ensuring your engine maintains optimal performance and efficiency.
It serves as a direct replacement for Yamaha OEM part 6FM-12411-00-00 and aftermarket equivalent AM6FM-12411-00.
- Installs as a direct OEM-equivalent replacement.
- Built with corrosion-resistant metals for performance in both saltwater and freshwater.
- Includes one thermostat as shown in the package contents.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 6FM-12411-00-00 |
| Aftermarket | AM6FM-12411-00 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This thermostat is designed for the specified Yamaha 4-stroke outboard models.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | F20LMHB | 20 | 4-Stroke | 2018–2022 | 6FM-12411-00-00 | |
| Yamaha | F20LWB | 20 | 4-Stroke | 2018–2022 | 6FM-12411-00-00 | |
| Yamaha | F20LWHB | 20 | 4-Stroke | 2018–2022 | 6FM-12411-00-00 | |
| Yamaha | F20LWPB | 20 | 4-Stroke | 2018–2022 | 6FM-12411-00-00 | |
| Yamaha | F20LWPHB | 20 | 4-Stroke | 2018–2022 | 6FM-12411-00-00 | |
| Yamaha | F20SMHB | 20 | 4-Stroke | 2018–2022 | 6FM-12411-00-00 | |
| Yamaha | F20SWB | 20 | 4-Stroke | 2018–2022 | 6FM-12411-00-00 | |
| Yamaha | F20SWHB | 20 | 4-Stroke | 2018–2022 | 6FM-12411-00-00 | |
| Yamaha | F20SWPB | 20 | 4-Stroke | 2018–2022 | 6FM-12411-00-00 | |
| Yamaha | F25LC | 25 | 4-Stroke | 2016–2022 | 6FM-12411-00-00 | |
| Yamaha | F25LMHC | 25 | 4-Stroke | 2016–2022 | 6FM-12411-00-00 | |
| Yamaha | F25LWTC | 25 | 4-Stroke | 2017–2020 | 6FM-12411-00-00 | |
| Yamaha | F25LWC | 25 | 4-Stroke | 2016–2021 | 6FM-12411-00-00 | |
| Yamaha | F25LWHC | 25 | 4-Stroke | 2016–2021 | 6FM-12411-00-00 | |
| Yamaha | F25SMHC | 25 | 4-Stroke | 2016–2021 | 6FM-12411-00-00 | |
| Yamaha | F25SWC | 25 | 4-Stroke | 2016–2021 | 6FM-12411-00-00 | |
| Yamaha | F25SWHC | 25 | 4-Stroke | 2016–2021 | 6FM-12411-00-00 | |
| Yamaha | F25SC | 25 | 4-Stroke | 2022 | 6FM-12411-00-00 | |
| Yamaha | F25SWTC | 25 | 4-Stroke | 2022 | 6FM-12411-00-00 | |
| Yamaha | F25SWTHC | 25 | 4-Stroke | 2022 | 6FM-12411-00-00 | |
| Yamaha | T25LWTC | 25 | 4-Stroke | 2019–2021 | 6FM-12411-00-00 | |
| Yamaha | T25XWTC | 25 | 4-Stroke | 2019–2021 | 6FM-12411-00-00 |
Technical Specs
- Product Type
- Outboard Engine Thermostat
- Installation
- Direct OEM Replacement
- Housing Material
- Corrosion-Resistant Metal
- Housing Color
- Brass/Metallic
- Fitting Type
- Direct Fit
- Operating Temperature
- 60°C (140°F)
- Other Technical Attributes
- Designed for both saltwater and freshwater environments
What’s in the Box
- 1 x Thermostat (6FM-12411-00-00)
Installation Notes
- Ensure the engine is off and cool. Disconnect the battery for safety.
- Locate the thermostat housing on the cylinder head or block. Place a drain pan underneath if needed.
- Carefully remove the bolts securing the housing cover. You may need to gently tap the cover to break the seal.
- Note the orientation of the old thermostat before removing it and its gasket or seal.
- Thoroughly clean the mating surfaces of the housing and its cover, removing all old gasket material.
- Install the new thermostat in the correct orientation, followed by the new gasket.
- Re-attach the housing cover and tighten the bolts evenly to the manufacturer's specified torque.
- Refill the cooling system as needed and check for any leaks after starting the engine.
Troubleshooting & FAQ
What are the signs of a faulty outboard thermostat?
Common symptoms include the engine overheating at various speeds, an alarm sounding, or the engine failing to warm up to its proper operating temperature. An erratic temperature gauge reading can also indicate a problem.
How can I test if my current thermostat is working?
You can remove the thermostat and suspend it in a pot of water with a thermometer. Heat the water and observe the temperature at which the thermostat begins to open. This part should open at approximately 140°F (60°C). If it doesn't open or stays stuck open, it needs replacement.
Is a gasket included with this thermostat?
This listing is for the thermostat only. Gaskets are typically sold separately. Always use a new gasket during installation to ensure a proper seal.
Why is a 140°F / 60°C temperature rating important?
This rating ensures the engine warms up quickly and maintains a consistent temperature for optimal fuel efficiency, performance, and reduced engine wear. Using the wrong temperature can lead to poor performance or damage.
What is the difference between an OEM and an aftermarket part?
This listing is an aftermarket replacement (not OEM). It is built to OEM-level specifications with comparable materials. All our parts are manufactured in an ISO 9002 facility and are batch-inspected for quality and consistency.
How fast is shipping and what does it cost?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free to most regions, 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 marine 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. See our policy page or reach out for instructions.
Safety & Important Info
- Verify images and specifications against your original part before ordering. If anything differs—even if your model appears in a compatibility list—do not purchase.
- This is an aftermarket replacement component, not an Original Equipment Manufacturer (OEM) part.
- Professional installation is recommended for safety and to ensure peak performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world conditions.
- Fast Global Fulfillment — We offer free standard delivery to most regions, with typical transit times of just 5–15 days.
- Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without compromising on materials or quality control.
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