Thermostat with Seal, 143°F (62°C) – Fits Yamaha 2-Stroke Outboards 9.9–55 HP, Replaces 6F5-12411-03-00
Thermostat with Seal, 143°F (62°C) – Fits Yamaha 2-Stroke Outboards 9.9–55 HP, Replaces 6F5-12411-03-00 is backordered and will ship as soon as it is back in stock.
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Thermostat with Seal, 143°F (62°C) – Fits Yamaha 2-Stroke Outboards...
Thermostat with Seal, 143°F (62°C) – Fits Yamaha 2-Stroke Outboards 9.9–55 HP, Replaces 6F5-12411-03-00 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket replacement thermostat with seal is designed for selected Yamaha 2-stroke outboard engines from 9.9 HP through 55 HP. It is specified for an operating temperature of 143°F (62°C) and replaces Yamaha OEM part number 6F5-12411-03-00.
The thermostat helps regulate engine operating temperature by controlling coolant flow through the cooling system. Confirm the exact model, year, and original part number before ordering, because Yamaha used different thermostats across similar horsepower ranges and production years.
- Aftermarket replacement thermostat for selected Yamaha 2-stroke outboards.
- 143°F (62°C) operating-temperature rating.
- Seal included for installation.
- Replaces Yamaha OEM part number 6F5-12411-03-00.
Part Number References
| Brand | Part Number | Reference |
|---|---|---|
| Yamaha | 6F5-12411-03-00 | OEM replacement reference |
| Sierra | 18-3632 | Aftermarket catalog reference for this thermostat |
Engine & Model Compatibility
The catalog-listed applications below are Yamaha 2-stroke outboards using the 6F5-12411-03-00 thermostat reference. Model suffixes, production years, and applications must remain together when checking fitment.
| Brand | Model(s) | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Yamaha | 9.9EL, 9.9ES | 9.9 | 2-Stroke | 1986–1995 | 6F5-12411-03-00 |
| Yamaha | 9.9L, 9.9S | 9.9 | 2-Stroke | 1986–1990 | 6F5-12411-03-00 |
| Yamaha | 9.9M | 9.9 | 2-Stroke | 1991–1995 | 6F5-12411-03-00 |
| Yamaha | 15EL, 15ES | 15 | 2-Stroke | 1986–1995 | 6F5-12411-03-00 |
| Yamaha | 15L, 15S | 15 | 2-Stroke | 1986–1990 | 6F5-12411-03-00 |
| Yamaha | 15ML, 15MS | 15 | 2-Stroke | 1991–1995 | 6F5-12411-03-00 |
| Yamaha | C25EL | 25 | 2-Stroke | 1991–1997 | 6F5-12411-03-00 |
| Yamaha | C25ML | 25 | 2-Stroke | 1993–1997 | 6F5-12411-03-00 |
| Yamaha | C25MS | 25 | 2-Stroke | 1992–1997 | 6F5-12411-03-00 |
| Yamaha | CV25EL, CV25EM | 25 | 2-Stroke | 1990 | 6F5-12411-03-00 |
| Yamaha | C30EL | 30 | 2-Stroke | 1991–1992 | 6F5-12411-03-00 |
| Yamaha | CV30EL | 30 | 2-Stroke | 1989–1990 | 6F5-12411-03-00 |
| Yamaha | C40EL | 40 | 2-Stroke | 1991–1997 | 6F5-12411-03-00 |
| Yamaha | C40MS, C40PL | 40 | 2-Stroke | 1992–1997 | 6F5-12411-03-00 |
| Yamaha | C40ML | 40 | 2-Stroke | 1994–1995 | 6F5-12411-03-00 |
| Yamaha | CV40EL | 40 | 2-Stroke | 1990 | 6F5-12411-03-00 |
| Yamaha | C55EL | 55 | 2-Stroke | 1991–1995 | 6F5-12411-03-00 |
| Yamaha | C55TL | 55 | 2-Stroke | 1993–1995 | 6F5-12411-03-00 |
| Yamaha | CV55EL | 55 | 2-Stroke | 1989 | 6F5-12411-03-00 |
Technical Specifications
- Product Type
- Thermostat with seal
- Application
- Selected Yamaha 2-stroke outboard cooling systems
- Operating Temperature
- 143°F (62°C)
- OEM Replacement
- Yamaha 6F5-12411-03-00
- Aftermarket Reference
- Sierra 18-3632
- Package Contents
- One thermostat and one seal
What’s in the Box
- 1 × Thermostat
- 1 × Installation seal
Installation Notes
- Allow the outboard to cool completely before beginning work.
- Disconnect the battery if the engine is equipped with an electrical starting system.
- Locate the thermostat cover and place a drain pan beneath the work area.
- Remove the cover carefully and note the orientation of the old thermostat.
- Remove the old thermostat and seal, then clean the mating surfaces without scratching them.
- Install the replacement thermostat in the same orientation as the original and fit the included seal.
- Reinstall the cover and tighten fasteners to the torque specified in the engine service manual.
- Run the engine in a suitable water supply, confirm normal water discharge, and check the cover for leaks.
Troubleshooting & FAQ
What are the symptoms of a faulty outboard thermostat?
A thermostat that is stuck closed can contribute to overheating, while one that is stuck open can cause the engine to run below its intended operating temperature. Reduced performance, an abnormal temperature indication, or an engine that does not warm normally can also indicate a cooling-system problem.
Does the package include the seal?
Yes. This listing includes one thermostat and one installation seal.
Is this an OEM Yamaha part?
No. This is an aftermarket replacement for Yamaha OEM part number 6F5-12411-03-00.
How do I confirm fitment?
Match your complete engine model, year, stroke, and original thermostat number with the compatibility information above. Do not rely on horsepower alone, because different Yamaha engines can use different thermostat applications.
Safety & Important Information
- Install only when the engine is cool and follow the service manual for your exact model.
- Verify the model, year, stroke, and original part number before purchase.
- Do not operate the outboard without an adequate water supply.
- This is an aftermarket replacement, not an OEM Yamaha component.
- Professional installation is recommended when the cooling system or thermostat housing is damaged.
About Sea Sierra
- Marine Replacement Parts — Practical aftermarket components for routine marine maintenance and repair.
- Fitment-Focused Listings — Compatibility information is organized by model, year, horsepower, and stroke where available.
- Support for Your Repair — Compare the original component and service-manual information before installation.
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