Thermostat (60°C/140°F) – Fits Yamaha 4-Stroke, Honda Outboard (Replaces 66M-12411-01, 6G8-12411-00, 19300-ZW9-003)
Thermostat (60°C/140°F) – Fits Yamaha 4-Stroke, Honda Outboard (Replaces 66M-12411-01, 6G8-12411-00, 19300-ZW9-003) 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.
International delivery times may vary due to customs processing.
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Thermostat (60°C/140°F) – Fits Yamaha 4-Stroke, Honda Outboard (Rep...
Thermostat (60°C/140°F) – Fits Yamaha 4-Stroke, Honda Outboard (Replaces 66M-12411-01, 6G8-12411-00, 19300-ZW9-003) is backordered and will ship as soon as it is back in stock.
Product Details
This Thermostat (60°C/140°F) – Fits Yamaha 4-Stroke 2.5-100 HP is an essential engine component designed to maintain optimal operating temperature. It is engineered for a wide range of Yamaha 4-Stroke outboards from 2.5 to 100 HP (1985–2018) and also fits various Honda 4-Stroke outboard models from 8 to 225 HP.
It serves as a direct replacement for multiple OEM and aftermarket part numbers, including Yamaha 66M-12411-01 / 6G8-12411-03, Honda 19300-ZW9-003, and Sierra 18-3541 / 18-3628.
- Engineered for direct-fit installation.
- Opens at a consistent 60°C (140°F) to regulate engine temperature.
- Includes the thermostat and required thermostat seal for a complete installation.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 66M-12411-00-00 |
| Yamaha | 66M-12411-01-00 |
| Yamaha | 6G8-12411-00-00 |
| Yamaha | 6G8-12411-01-00 |
| Yamaha | 6G8-12411-02-00 |
| Yamaha | 6G8-12411-03-00 |
| Honda | 19300-ZW9-003 |
| Honda | 19300-881-741 |
| Honda | 19300-921-003 |
| Sierra | 18-3541 |
| Sierra | 18-3628 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Yamaha engines, this part fits a wide array of 4-stroke models manufactured between 1985 and 2005. Check specific model details below.
For Honda outboards, compatibility extends across numerous BF-series models. Please verify your specific model code against the list.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Yamaha | F2.5 | 2.5 | 4-Stroke | 66M-12411-01-00 | |
| Yamaha | F4, F4A | 4 | 4-Stroke | 66M-12411-01-00 | |
| Yamaha | F6, F6A | 6 | 4-Stroke | 2001–2005 | 66M-12411-01-00 |
| Yamaha | F8, T8 | 8 | 4-Stroke | 2001–2005 | 66M-12411-01-00 |
| Yamaha | F9.9, T9.9 | 9.9 | 4-Stroke | 1985–2005 | 66M-12411-01-00 |
| Yamaha | F15 | 15 | 4-Stroke | 1998–2005 | 66M-12411-01-00 |
| Yamaha | F25, T25 | 25 | 4-Stroke | 1998–2005 | 66M-12411-01-00 |
| Yamaha | F30 | 30 | 4-Stroke | 2001–2005 | 66M-12411-01-00 |
| Yamaha | F40 (4-cyl) | 40 | 4-Stroke | 1999 | 66M-12411-01-00 |
| Yamaha | F40 (3-cyl) | 40 | 4-Stroke | 2000–2005 | 66M-12411-01-00 |
| Yamaha | F50, T50 | 50 | 4-Stroke | 1995–2005 | 66M-12411-01-00 |
| Yamaha | F60, T60 | 60 | 4-Stroke | 2002–2005 | 66M-12411-01-00 |
| Yamaha | F70 | 70 | 4-Stroke | 66M-12411-01-00 | |
| Yamaha | F80 | 80 | 4-Stroke | 1999–2000 | 66M-12411-01-00 |
| Yamaha | F100 | 100 | 4-Stroke | 1999–2000 | 66M-12411-01-00 |
| Honda | BF8D1, BF8D2, BF8D3 | 8 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF15D3, BF15D4, BF15D5, BF15D6, BF15DK0 | 15 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF20D3, BF20D4, BF20D5, BF20D6, BF20DK0 | 20 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF25D4, BF25D5, BF25D6, BF25DK0 | 25 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF30D4, BF30D5, BF30D6, BF30DK0 | 30 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF40A4, BF40A5, BF40A6, BF40AK0, BF40D | 40 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF50A4, BF50A5, BF50A6, BF50AK0, BF50D | 50 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF60A, BFP60A | 60 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF75DK0 | 75 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF90DK0 | 90 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF200A2 | 200 | 4-Stroke | 19300-ZW9-003 | |
| Honda | BF225A2 | 225 | 4-Stroke | 19300-ZW9-003 |
Technical Specs
- Product Type
- Engine Thermostat
- Installation
- Direct Replacement
- Temperature Rating
- 60°C (140°F)
- Housing Material
- Metal
- Fitting Type
- Direct Fit
- Operating Temperature
- 60°C (140°F) opening temperature
- Package Contents
- Thermostat and Thermostat Seal
What’s in the Box
- 1 x Thermostat (Replaces 66M-12411-00/66M-12411-01)
- 1 x Thermostat Seal (Replaces 688-12412)
Installation Notes
- Ensure the engine is completely cool before beginning work.
- Locate the thermostat housing on the engine block or cylinder head.
- Disconnect any hoses attached to the housing and drain the remaining coolant into a suitable container.
- Remove the mounting bolts securing the thermostat housing cover.
- Carefully lift the cover and remove the old thermostat and its seal or gasket.
- Thoroughly clean both the housing and cover mating surfaces to remove any old gasket material or corrosion.
- Install the new thermostat and seal in the correct orientation.
- Re-secure the housing cover and tighten the bolts to the manufacturer’s specified torque.
- Reconnect hoses, refill the cooling system, and run the engine to check for leaks and proper temperature.
Troubleshooting & FAQ
How do I know if my thermostat needs replacing?
Common signs of a faulty thermostat include engine overheating (stuck closed) or taking too long to reach operating temperature (stuck open). You may also notice poor engine performance or an increase in fuel consumption.
What is the purpose of the 60°C (140°F) temperature rating?
This rating indicates the temperature at which the thermostat begins to open, allowing coolant to circulate through the engine. It is calibrated to match OEM specifications for optimal engine performance and longevity in marine environments.
Is the thermostat seal included with this part?
Yes, this kit includes both the thermostat and the corresponding thermostat seal (gasket) for a complete and proper installation.
Can I use this thermostat if my engine model isn't listed?
We do not recommend it. For proper cooling and engine performance, only use this thermostat if your specific engine model and year are listed as compatible. Using the wrong part can lead to engine damage.
What happens if I don't replace the thermostat seal?
The seal ensures a coolant-tight fit. Reusing an old seal or not using one can lead to coolant leaks, which can cause the engine to overheat and sustain serious damage. Always use the new seal provided.
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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