Thermostat (60°C/140°F) – Fits Yamaha 4-Stroke 2.5-80 HP Outboards (Replaces 66M-12411-01-00, 66M-12411-00-00)
Thermostat (60°C/140°F) – Fits Yamaha 4-Stroke 2.5-80 HP Outboards (Replaces 66M-12411-01-00, 66M-12411-00-00) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
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Thermostat (60°C/140°F) – Fits Yamaha 4-Stroke 2.5-80 HP Outboards ...
Thermostat (60°C/140°F) – Fits Yamaha 4-Stroke 2.5-80 HP Outboards (Replaces 66M-12411-01-00, 66M-12411-00-00) is backordered and will ship as soon as it is back in stock.
Product Details
This replacement Thermostat (60°C/140°F) – Fits Yamaha 4-Stroke 2.5-80 HP Outboards and is designed to regulate engine temperature for optimal performance and longevity. It is engineered for a wide range of Yamaha 4-stroke outboard models from 2.5 HP up to 150 HP.
This part is a direct interchange for Yamaha OEM part numbers 66M-12411-01-00, 66M-12411-00-00, 6G8-12411-03-00, 6G8-12411-02-00, 6G8-12411-01-00, and 6G8-12411-00-00.
- Installs as a direct replacement for the original OEM thermostat.
- Opens at a consistent 60°C (140°F) to maintain correct operating temperature.
- Features a small relief hole to improve water circulation and cooling at idle speeds.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By |
|---|---|---|
| Yamaha | 6G8-12411-00-00 | 6G8-12411-01-00 |
| Yamaha | 6G8-12411-01-00 | 6G8-12411-02-00 |
| Yamaha | 6G8-12411-02-00 | 6G8-12411-03-00 |
| Yamaha | 6G8-12411-03-00 | 66M-12411-00-00 |
| Yamaha | 66M-12411-00-00 | 66M-12411-01-00 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | F2.5 | 2.5 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F4 | 4 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F4A/F4B | 4 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F5A | 5 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F6C | 6 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F8 | 8 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F9.9C | 9.9 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | FT9.9D | 9.9 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F13.5A | 13.5 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F15 | 15 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F15A | 15 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F30 | 30 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F40 | 40 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F40A | 40 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F50 | 50 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | T50 | 50 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F60 | 60 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | T60 | 60 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F70 | 70 | 4-Stroke | 2011–2018 | 66M-12411-01-00 | Supersedes 66M-12411-00-00 |
| Yamaha | F70LA | 70 | 4-Stroke | 2011–2018 | 66M-12411-01-00 | Supersedes 66M-12411-00-00 |
| Yamaha | F75 | 75 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F80 | 80 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F90 | 90 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | F100 | 100 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | FL150 | 150 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 | |
| Yamaha | LF150 | 150 | 4-Stroke | 66M-12411-01-00 | Supersedes 66M-12411-00-00 |
Technical Specs
- Product Type
- Thermostat
- Installation
- Direct replacement
- Operating Temperature
- 60°C (140°F)
- Housing Color
- Silver/metallic
- Other Technical Attributes
- Contains small relief hole for improved idle operation
What’s in the Box
- 1 x Thermostat (66M-12411-01-00)
Installation Notes
- Ensure the engine is completely cool and disconnect the battery for safety.
- Place a drain pan under the engine and drain the cooling system.
- Locate the thermostat housing on the engine block or cylinder head.
- Remove the bolts securing the housing cover. Note their placement if they are different lengths.
- Carefully remove the old thermostat and the gasket or O-ring. Keep note of its orientation.
- Thoroughly clean both the housing and cover mating surfaces to remove any old gasket material or corrosion.
- Install the new thermostat in the same orientation as the original. Ensure it is correctly seated.
- Install the new gasket or O-ring, then re-attach the housing cover and tighten the bolts to the manufacturer's specified torque.
- Refill the cooling system with the recommended coolant.
- Reconnect the battery, start the engine, and let it warm up. Check for any leaks around the thermostat housing.
Troubleshooting & FAQ
How do I know if my thermostat is failing?
Common signs of a faulty thermostat include the engine overheating at low speeds, or taking too long to reach operating temperature. You may also see temperature warnings on your gauge or inconsistent temperature readings. An engine running too cold can cause poor fuel economy and carbon buildup.
What is the purpose of the small hole in this thermostat?
The small hole, sometimes called a jiggle pin or bleed hole, allows a small amount of water to bypass the thermostat even when it's closed. This helps bleed trapped air from the cooling system and improves cooling water circulation at idle speeds.
Can I test my old thermostat before replacing it?
Yes. You can suspend the old thermostat in a pot of water with a thermometer. Heat the water and observe the temperature at which the thermostat begins to open. For this model, it should start opening around 60°C (140°F). If it doesn't open, or opens at a significantly different temperature, it should be replaced.
My engine model is listed, but the part photo looks slightly different. What should I do?
Always verify by comparing the photos and part numbers to your existing part. If there are any discrepancies, do not purchase. Contact us with your engine's full model and serial number, and we can help confirm the correct fitment.
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.
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