60°C/140°F Engine Thermostat with Seal – Fits Select Yamaha and Honda 4-Stroke Outboards
60°C/140°F Engine Thermostat with Seal – Fits Select Yamaha and Honda 4-Stroke Outboards is backordered and will ship as soon as it is back in stock.
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60°C/140°F Engine Thermostat with Seal – Fits Select Yamaha and Hon...
60°C/140°F Engine Thermostat with Seal – Fits Select Yamaha and Honda 4-Stroke Outboards is backordered and will ship as soon as it is back in stock.
Product Details
This 60°C/140°F engine thermostat with seal is an aftermarket replacement component for selected Yamaha and Honda 4-stroke outboard cooling systems. The thermostat helps regulate engine operating temperature by beginning to open at approximately 60°C (140°F), subject to the specifications of the applicable engine.
Commonly cross-referenced numbers include Yamaha 66M-12411-00-00, 66M-12411-01-00, 6G8-12411-00-00, 6G8-12411-01-00, 6G8-12411-02-00 and 6G8-12411-03-00; Honda 19300-ZW9-003, 19300-881-741 and 19300-921-003; and Sierra 18-3541 and 18-3628. Always compare the original thermostat, seal, engine model and serial-number range before ordering.
- Aftermarket replacement engine thermostat.
- Approximate opening temperature: 60°C (140°F).
- Includes one thermostat and one matching thermostat seal.
- Designed for direct replacement where the listed part number and engine application match.
Part Number Matrix
The following references are provided for identification and cross-reference purposes. A number match should be confirmed against the exact engine model and serial-number range.
| 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 and Model Compatibility
The following applications are commonly associated with the listed thermostat references. Model designations, production years, serial ranges and component revisions can affect fitment, so verify the exact engine identification before installation.
| Brand | Model | Rated HP | Stroke | Years or Notes | Reference |
|---|---|---|---|---|---|
| Yamaha | F2.5 | 2.5 | 4-Stroke | Verify model revision | 66M-12411-01-00 |
| Yamaha | F4, F4A | 4 | 4-Stroke | Verify model revision | 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, 3-cylinder and 4-cylinder versions | 40 | 4-Stroke | Verify year and engine configuration | 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 | Verify model revision | 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 | Verify model revision | 19300-ZW9-003 |
| Honda | BF15D3, BF15D4, BF15D5, BF15D6, BF15DK0 | 15 | 4-Stroke | Verify model revision | 19300-ZW9-003 |
| Honda | BF20D3, BF20D4, BF20D5, BF20D6, BF20DK0 | 20 | 4-Stroke | Verify model revision | 19300-ZW9-003 |
| Honda | BF25D4, BF25D5, BF25D6, BF25DK0 | 25 | 4-Stroke | Verify model revision | 19300-ZW9-003 |
| Honda | BF30D4, BF30D5, BF30D6, BF30DK0 | 30 | 4-Stroke | Verify model revision | 19300-ZW9-003 |
| Honda | BF40A4, BF40A5, BF40A6, BF40AK0, BF40D | 40 | 4-Stroke | Verify model revision | 19300-ZW9-003 |
| Honda | BF50A4, BF50A5, BF50A6, BF50AK0, BF50D | 50 | 4-Stroke | Verify model revision | 19300-ZW9-003 |
| Honda | BF60A, BFP60A | 60 | 4-Stroke | Verify model revision | 19300-ZW9-003 |
| Honda | BF75DK0 | 75 | 4-Stroke | Verify model revision | 19300-ZW9-003 |
| Honda | BF90DK0 | 90 | 4-Stroke | Verify model revision | 19300-ZW9-003 |
| Honda | BF200A2 | 200 | 4-Stroke | Verify model revision | 19300-ZW9-003 |
| Honda | BF225A2 | 225 | 4-Stroke | Verify model revision | 19300-ZW9-003 |
Technical Specifications
- Product Type
- Engine thermostat with seal
- Replacement Type
- Aftermarket direct replacement where application matches
- Opening Temperature
- Approximately 60°C (140°F)
- Application
- Selected Yamaha and Honda 4-stroke outboards
- Package Contents
- One thermostat and one thermostat seal
What's in the Box
- 1 × 60°C/140°F engine thermostat
- 1 × thermostat seal
Installation Notes
- Allow the engine to cool completely before servicing the cooling system.
- Confirm the engine model, serial-number range and original thermostat reference before removing parts.
- Locate the thermostat housing and place a suitable container beneath the work area.
- Remove the housing cover and carefully remove the old thermostat and seal.
- Clean the mating surfaces without damaging the housing or cylinder-head sealing area.
- Install the replacement thermostat and supplied seal in the same orientation as the original component.
- Reinstall the housing cover and tighten fasteners to the engine manufacturer's specified torque.
- Reconnect any hoses, restore the cooling system as required and inspect for leaks.
- Run the engine according to the manufacturer's procedure and confirm proper water flow and operating temperature.
Troubleshooting and FAQ
How do I know if the thermostat needs replacing?
Possible symptoms include overheating, unusually slow warm-up, unstable operating temperature or reduced cooling-system performance. These symptoms can also have other causes, so inspect the water passages, water pump, hoses and sensors as appropriate.
What does the 60°C (140°F) rating mean?
It identifies the approximate temperature at which the thermostat begins to open. The actual operating temperature and test procedure depend on the engine design and manufacturer specifications.
Is the thermostat seal included?
Yes. This product is supplied with one thermostat and one matching thermostat seal.
Can I use it if my exact engine model is not listed?
Do not assume fitment from horsepower alone. Confirm the exact model designation, year or serial-number range, original part number and thermostat dimensions before ordering.
Why should the old seal not be reused?
An aged or damaged seal may not provide a reliable coolant-tight joint. Replace it with the supplied seal when the housing is serviced and follow the engine manufacturer's installation instructions.
Is this an OEM thermostat?
No. This is an aftermarket replacement. OEM and aftermarket reference numbers are shown only for identification and application comparison.
Safety and Important Information
- Verify the engine model, year or serial range, original part number and the physical dimensions before purchase.
- Do not work on a hot engine or pressurized cooling system.
- Use the correct coolant, sealing method and fastener torque specified for your engine.
- Professional installation is recommended if you are not familiar with outboard cooling-system service.
- This listing is for the thermostat and seal only; no additional housing, bolts, hoses or coolant are included.
About Sea Sierra
- Marine Replacement Parts — Practical aftermarket components for maintenance and repair applications.
- Application-Focused Listings — Reference numbers and model information are provided to support compatibility checks.
- Customer Support — Contact support with your engine model and original part details if you need help comparing applications.
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