Thermostat (60°C) – Fits Yamaha F20, F25C Outboards (Replaces 6FM-12411-00-00)
Thermostat (60°C) – Fits Yamaha F20, F25C Outboards (Replaces 6FM-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 aftermarket Thermostat (60°C) is engineered to regulate engine temperature in Yamaha F20 (2018–Up) and F25C (2016–Up) 4-stroke outboard motors. It maintains a consistent operating temperature by opening at 60°C (140°F) to ensure optimal performance.
It serves as a direct cross-reference for Yamaha OEM part number 6FM-12411-00-00.
- Designed for direct installation as an internal engine component.
- Critical for preventing engine overheating and maintaining fuel efficiency.
- Package includes one thermostat, ready for installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Notes |
|---|---|---|
| Yamaha | 6FM-12411-00-00 |
Engine & Model Compatibility
Confirm your engine model and year in the table below.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | F20 | 20 | 4-Stroke | 2018–Up | 6FM-12411-00-00 | |
| Yamaha | F25C | 25 | 4-Stroke | 2016–Up | 6FM-12411-00-00 |
Technical Specs
- Product Type
- Thermostat
- Installation
- Internal Engine Component
- Opening Temperature
- 60°C (140°F)
- Housing Color
- Silver/Metallic
- Approx. Dimensions
- 6.0 in x 6.0 in x 6.0 in
- Weight
- 40.8g (1.44 oz)
- Quality Standard
- Meets OEM Specifications
- Warranty
- Covered by Manufacturer Standard Warranty
What’s in the Box
- 1 x Thermostat (Replaces 6FM-12411-00-00)
Installation Notes
- Ensure the engine is completely cool before beginning. Disconnect the negative battery terminal for safety.
- Locate the thermostat housing on the engine block, typically at the top where the main coolant hose connects.
- Place a drain pan under the housing and slowly loosen the retaining bolts to allow coolant to drain safely.
- Once drained, remove the housing cover and take note of the old thermostat's orientation before removing it.
- Remove the old gasket and thoroughly clean both mating surfaces of the housing and engine block.
- Install the new thermostat in the correct orientation. A new gasket (not included) should be placed on the housing.
- Reinstall the housing cover and tighten the bolts to the manufacturer's recommended torque specification.
- Refill the cooling system with the appropriate type and amount of coolant. Reconnect the battery.
- Start the engine and let it run, carefully checking for any signs of leaks around the housing. Monitor the temperature gauge to ensure it operates in the normal range.
Troubleshooting & FAQ
How do I know if my thermostat is failing?
Common signs of a faulty thermostat include engine overheating, the temperature gauge reading abnormally high or low, poor heater performance, and potential coolant leaks around the thermostat housing.
What is the correct operating temperature for this part?
This thermostat is rated to begin opening at 60°C (140°F). This allows coolant to circulate from the radiator to maintain the engine's optimal operating temperature.
Is this a complete kit with gaskets?
This listing includes the thermostat only. Gaskets or seals are sold separately. We highly recommend installing a new gasket to ensure a leak-proof seal.
Can a faulty thermostat cause permanent engine damage?
Yes, a thermostat stuck in the closed position can cause severe overheating, leading to significant engine damage like a blown head gasket. A thermostat stuck open can prevent the engine from reaching proper operating temperature, affecting performance and efficiency.
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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