Yamaha Thermostat Replacement – 4-Stroke Outboards 2.5–100 HP – Replaces Yamaha 66M-12411-01-00
Yamaha Thermostat Replacement – 4-Stroke Outboards 2.5–100 HP – Replaces Yamaha 66M-12411-01-00 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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Yamaha Thermostat Replacement – 4-Stroke Outboards 2.5–100 HP – Rep...
Yamaha Thermostat Replacement – 4-Stroke Outboards 2.5–100 HP – Replaces Yamaha 66M-12411-01-00 is backordered and will ship as soon as it is back in stock.
Product Details
This thermostat replacement is designed to regulate coolant flow and help maintain the proper operating temperature of compatible Yamaha 4-Stroke outboard engines. The listed application range covers Yamaha models from 2.5 HP through 100 HP, but model, year, serial-number, and regional variations can affect fitment. Confirm the part number and engine details before ordering.
This aftermarket replacement is identified as a replacement for Yamaha OEM part 66M-12411-01-00. It is intended for use in the engine cooling system and should be compared with the original thermostat before installation.
- Replacement thermostat for selected Yamaha 4-Stroke outboards.
- Designed to begin opening at approximately 60°C (140°F).
- Helps control coolant circulation and engine operating temperature.
- Verify the original part number, engine model, year, and serial number before purchase.
Part Number References
The following references are associated with this replacement. Part-number matching alone does not replace complete engine fitment verification.
| Brand or source | Part number |
|---|---|
| Yamaha OEM reference | 66M-12411-01-00 |
| GHmarine aftermarket reference | 66M-12411 |
| PWCParts reference | 66M-12411-01-00 |
Engine & Model Compatibility
The applications below reflect the supplied application list for the referenced thermostat. Yamaha fitment may vary by model designation, production year, serial-number range, and market. Confirm your engine identification and service-manual part number before installation.
| Brand | Model | Rated HP | Stroke | Listed years | OEM reference | Notes |
|---|---|---|---|---|---|---|
| Yamaha | F2.5 | 2.5 | 4-Stroke | 2003–2023 | 66M-12411-01-00 | Verify exact model and serial number. |
| Yamaha | F4/F4A | 4 | 4-Stroke | 1999–2016 | 66M-12411-01-00 | Verify exact model and serial number. |
| Yamaha | F6/F6A | 6 | 4-Stroke | 2000–2016 | 66M-12411-01-00 | Verify exact model and serial number. |
| Yamaha | F8/T8 | 8 | 4-Stroke | 2001–2016 | 66M-12411-01-00 | Verify exact model and serial number. |
| Yamaha | F9.9/T9.9 | 9.9 | 4-Stroke | 1985–2023 | 66M-12411-01-00 | Multiple model variants; confirm before ordering. |
| Yamaha | F15/T15 | 15 | 4-Stroke | 1998–2023 | 66M-12411-01-00 | Verify exact model and serial number. |
| Yamaha | F25/T25 | 25 | 4-Stroke | 1998–2019 | 66M-12411-01-00 | Verify exact model and serial number. |
| Yamaha | F30 | 30 | 4-Stroke | 2001–2023 | 66M-12411-01-00 | Verify exact model and serial number. |
| Yamaha | F40/T40 | 40 | 4-Stroke | 1999–2023 | 66M-12411-01-00 | Includes listed variants such as F40A and F40B; confirm details. |
| Yamaha | F50/T50 | 50 | 4-Stroke | 1995–2023 | 66M-12411-01-00 | Verify exact model and serial number. |
| Yamaha | F60/T60 | 60 | 4-Stroke | 2002–2023 | 66M-12411-01-00 | Verify exact model and serial number. |
| Yamaha | F70 | 70 | 4-Stroke | 2010–2023 | 66M-12411-01-00 | Verify exact model and serial number. |
| Yamaha | F80 | 80 | 4-Stroke | Not specified | 66M-12411-01-00 | Confirm the application in the engine service documentation. |
| Yamaha | F100 | 100 | 4-Stroke | Up to 2000 | 66M-12411-01-00 | Confirm the applicable production range. |
Technical Specifications
- Product type
- Thermostat replacement
- Application
- Selected Yamaha 4-Stroke outboard engines
- Opening temperature
- Approximately 60°C (140°F)
- Installation
- Replacement installation using the original thermostat location and hardware as applicable
- Housing material
- Metal
- Housing color
- Silver/metallic
- OEM reference
- Yamaha 66M-12411-01-00
What’s in the Box
- 1 × thermostat replacement
A gasket, seal, bolts, or other installation hardware is not listed as included. Reuse or replace these items only as appropriate for the engine manufacturer’s service instructions.
Installation Notes
- Allow the engine to cool completely before beginning work.
- Disconnect the battery or otherwise prevent accidental engine starting.
- Follow the engine service manual for cooling-system draining requirements.
- Locate the thermostat housing and remove the cover using the correct tools.
- Note the orientation of the original thermostat before removal.
- Inspect and clean the mating surfaces without damaging the housing.
- Install the replacement thermostat in the correct orientation.
- Install a new gasket or seal when required by the service manual; no gasket is listed as included.
- Reinstall the housing cover and tighten fasteners to the manufacturer’s specification.
- Restore the cooling system as specified for the engine.
- Start the engine according to the manufacturer’s procedure and check for leaks or abnormal temperature behavior.
Troubleshooting & FAQ
How do I know if a thermostat may be failing?
Possible symptoms include overheating, slow warm-up, unstable temperature readings, or abnormal cooling-system behavior. Diagnose the complete cooling system before replacing the thermostat.
What temperature does this thermostat open at?
The listed opening temperature is approximately 60°C (140°F). Actual testing should follow the engine manufacturer’s service procedure.
Does this thermostat fit every Yamaha outboard from 2.5 to 100 HP?
No broad horsepower range can replace exact fitment verification. Confirm the engine model, year, serial-number range, stroke, and OEM reference before ordering.
Does the package include a gasket?
No gasket is listed as included. Check the engine service manual and obtain the correct gasket or seal separately if required.
Can I test a thermostat before installation?
Thermostat testing may be possible in heated water with an accurate thermometer, but use the manufacturer’s specified testing method and temperature range. Do not damage the thermostat during testing.
Is this an OEM Yamaha part?
No. This is an aftermarket replacement associated with Yamaha OEM reference 66M-12411-01-00. It is not represented as a genuine Yamaha component.
What warranty or return coverage applies?
Warranty and returns are governed by the applicable seller policy and order terms. Review those terms before purchase and retain order documentation.
Safety & Important Information
- Work only on a fully cooled engine and follow the manufacturer’s safety instructions.
- Confirm the part number, engine model, year, serial number, and physical configuration before installation.
- Do not operate the engine if coolant leaks, overheating, or abnormal temperature behavior is present.
- Professional installation is recommended when the correct procedure or fitment is uncertain.
- This is an aftermarket replacement, not a genuine OEM Yamaha component.
About Sea Sierra
- Marine Replacement Parts — Parts selected for common service and replacement applications.
- Fitment-Focused Support — Compare the original part and verify engine details before ordering.
- Practical Value — Aftermarket alternatives for routine marine maintenance and repair.
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