60°C Thermostat for Yamaha F6A, F8B, F8C, FT8D, F9.9A, F9.9B, F9.9F, F9.9J, FT9.9G and FT9.9L Outboards
60°C Thermostat for Yamaha F6A, F8B, F8C, FT8D, F9.9A, F9.9B, F9.9F, F9.9J, FT9.9G and FT9.9L Outboards 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.
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60°C Thermostat for Yamaha F6A, F8B, F8C, FT8D, F9.9A, F9.9B, F9.9F...
60°C Thermostat for Yamaha F6A, F8B, F8C, FT8D, F9.9A, F9.9B, F9.9F, F9.9J, FT9.9G and FT9.9L Outboards is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket 60°C outboard thermostat is designed for the specified Yamaha four-stroke models. It helps regulate engine operating temperature and is supplied as a single thermostat for replacement of the original component.
The thermostat is listed as aftermarket reference 18-3541. Its primary Yamaha reference is 66M-12411-01, which supersedes Yamaha references 6G8-12411-00, 6G8-12411-01, 6G8-12411-02 and 6G8-12411-03.
- Single replacement thermostat
- Opening temperature: 60°C
- For the Yamaha four-stroke models listed below
- Aftermarket replacement; not a Yamaha-branded OEM component
Part Number References
Use the following references when comparing your original thermostat. Confirm the complete engine model before ordering.
| Brand | Reference | Description | Relationship |
|---|---|---|---|
| Aftermarket | 18-3541 | Thermostat | Aftermarket reference |
| Yamaha | 66M-12411-01 | Thermostat | Primary Yamaha reference |
| Yamaha | 6G8-12411-00 | Thermostat | Superseded reference |
| Yamaha | 6G8-12411-01 | Thermostat | Superseded reference |
| Yamaha | 6G8-12411-02 | Thermostat | Superseded reference |
| Yamaha | 6G8-12411-03 | Thermostat | Superseded reference |
Engine & Model Compatibility
The company fitment record specifies the following Yamaha four-stroke models. Model suffixes, year ranges and serial-number conditions can affect fitment, so compare your complete model designation with the information below and verify against the original thermostat or service documentation.
| Brand | Model | Stroke | Thermostat Temperature | Reference |
|---|---|---|---|---|
| Yamaha | F6A | 4-Stroke | 60°C | 66M-12411-01 |
| Yamaha | F8B | 4-Stroke | 60°C | 66M-12411-01 |
| Yamaha | F8C | 4-Stroke | 60°C | 66M-12411-01 |
| Yamaha | FT8D | 4-Stroke | 60°C | 66M-12411-01 |
| Yamaha | F9.9A, F9.9B, F9.9F, F9.9J | 4-Stroke | 60°C | 66M-12411-01 |
| Yamaha | FT9.9A, FT9.9G, FT9.9L | 4-Stroke | 60°C | 66M-12411-01 |
Technical Specifications
- Product Type
- Outboard thermostat
- Quantity
- 1 thermostat
- Opening Temperature
- 60°C
- Application
- Specified Yamaha four-stroke outboard models
- Aftermarket Reference
- 18-3541
- Primary Yamaha Reference
- 66M-12411-01
What's in the Box
- 1 × 60°C aftermarket thermostat
A gasket is not listed as an included component for this product. If your installation requires a replacement thermostat gasket, confirm the correct gasket separately for your exact engine model.
Installation Notes
- Allow the engine to cool completely before starting work.
- Disconnect the battery if required by your service procedure and keep the work area clean.
- Locate the thermostat housing and remove the cover according to the engine service manual.
- Remove the old thermostat and inspect the housing, sealing surfaces and related gasket.
- Clean the mating surfaces without damaging the housing.
- Install the replacement thermostat in the correct orientation for your specific Yamaha engine.
- Use the correct new gasket if the original gasket is damaged or the service manual requires replacement. A gasket is not included with this thermostat.
- Reinstall the housing cover and tighten fasteners to the manufacturer's specified torque.
- Run the engine according to the service procedure and check for leaks and correct cooling-system operation.
Troubleshooting & FAQ
What temperature does this thermostat open at?
This thermostat is specified with a 60°C opening temperature.
Is this a complete thermostat kit?
No. This listing is for one thermostat only. A gasket or O-ring is not listed as included.
Which Yamaha references does it replace?
The company reference lists Yamaha 66M-12411-01 as the primary reference and identifies 6G8-12411-00, 6G8-12411-01, 6G8-12411-02 and 6G8-12411-03 as superseded references.
Will it fit every Yamaha four-stroke outboard?
No. Fitment is limited to the specified models: F6A, F8B, F8C, FT8D, F9.9A, FT9.9A, F9.9B, F9.9F, F9.9J, FT9.9G and FT9.9L. Verify the complete model designation and original part before ordering.
Is this an OEM Yamaha thermostat?
No. This is an aftermarket replacement referenced against the listed Yamaha part numbers.
Safety & Important Information
- Work only on a cool engine and follow the applicable service manual.
- Confirm the complete model designation, stroke and original thermostat reference before purchase.
- Do not rely on horsepower range alone to determine fitment.
- Professional installation is recommended if you are unfamiliar with outboard cooling-system service.
About Sea Sierra
- Marine Replacement Parts — Practical aftermarket components for routine outboard maintenance and repair.
- Fitment-Focused Listings — Product references and specified applications are provided to help you compare the replacement with your original part.
- Installation Awareness — Always use the correct service procedure and replace related seals or gaskets when required by the engine manufacturer.
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