Yamaha Outboard Thermostat, 50°C (122°F) – 2-Stroke 3–250 HP and F15C/F20BF 4-Stroke Applications
Yamaha Outboard Thermostat, 50°C (122°F) – 2-Stroke 3–250 HP and F15C/F20BF 4-Stroke Applications is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Yamaha Outboard Thermostat, 50°C (122°F) – 2-Stroke 3–250 HP and F1...
Yamaha Outboard Thermostat, 50°C (122°F) – 2-Stroke 3–250 HP and F15C/F20BF 4-Stroke Applications is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket 50°C (122°F) thermostat is designed for selected Yamaha outboard applications, including Yamaha 2-stroke models from 3 HP through 250 HP and selected Yamaha 4-stroke F15C and F20BF models. It helps regulate engine operating temperature by opening at the specified 50°C rating.
The thermostat is supplied with the applicable seal or gasket for the listed application. It is not an OEM Yamaha component; use the reference numbers and exact model information below to confirm compatibility before ordering.
- 50°C (122°F) opening temperature.
- Aftermarket replacement thermostat for selected Yamaha outboard cooling systems.
- Applications include both specific 2-stroke and selected 4-stroke Yamaha models.
- Seal or thermostat-cover gasket included according to the applicable reference application.
Reference Part Numbers
The following manufacturer and aftermarket references are associated with the applications listed for this product. Part-number relationships can vary by engine model, year, and serial range, so confirm the complete engine specification before installation.
| Brand | Reference | Application note |
|---|---|---|
| Yamaha | 6E5-12411-02 | Selected small-outboard and 2-stroke applications; supersedes 6E5-12411-00 and 6E5-12411-01. |
| Sierra | 18-3623 | Aftermarket thermostat reference; seal included. |
| Yamaha | 6E5-12411-30 | Selected 2-stroke applications; supersedes 688-12411-10 and 688-12411-11. |
| Sierra | 18-3540 | Aftermarket thermostat reference; gasket included for the applicable installation. |
| Yamaha | 6H3-12411-11 | Selected 50G, 60F, and 70B 2-stroke applications. |
| Sierra | 18-3622 | Aftermarket reference associated with the 50G, 60F, and 70B applications. |
| Yamaha | 6AH-12411-00 | Selected 4-stroke F15C and F20BF applications. |
Engine Compatibility
Compatibility is grouped by the specific Yamaha application records associated with this thermostat. Do not rely on horsepower alone; verify the exact model and the original thermostat reference.
| Brand | Model or model group | Rated HP | Stroke | Reference |
|---|---|---|---|---|
| Yamaha | 3A / Malta, 4A, 4B, 5C, 6C, 6D, 8C, 20D, E25A, 25B, E25B, 25J, 25N, 25V, 30D, 30G, 30H, E30H, 40X, E40X | 3–40 | 2-Stroke | 6E5-12411-02; Sierra 18-3623 |
| Yamaha | 3, 4, 5, 6, 8 | 3–8 | 2-Stroke | 6E5-12411-02; Sierra 18-3623 |
| Yamaha | C30 | 30 | 2-Stroke, 1993 and newer | 6E5-12411-02; Sierra 18-3623 |
| Yamaha | 9.9F, 15F, 25N, 30D, 40V, 75C, 90A, 100A, 115C, 130B, 150F, 175D, 200F, 200G, 225D, 225G, 250A, 250B | 9.9–250 | 2-Stroke | 6E5-12411-30; Sierra 18-3540 |
| Yamaha | Z150P, Z150Q, Z175G, Z200N, Z200P | 150–200 | 2-Stroke HPDI | 6E5-12411-30; Sierra 18-3540 |
| Yamaha | 50G, 60F, 70B | 50–70 | 2-Stroke | 6H3-12411-11; Sierra 18-3622 |
| Yamaha | F15C, F20BF | 15–20 | 4-Stroke | 6AH-12411-00 |
Technical Specifications
- Product type
- Aftermarket outboard thermostat
- Opening temperature
- 50°C (122°F)
- Primary applications
- Selected Yamaha 2-stroke and 4-stroke outboards
- Installation
- Replacement installation in the original thermostat location
- OEM status
- Aftermarket replacement; not manufactured by Yamaha
What's in the Box
- 1 x 50°C outboard thermostat
- 1 x applicable thermostat seal or cover gasket
Installation Notes
- Allow the engine to cool completely before beginning work.
- Confirm that the replacement thermostat reference and engine application match your original part.
- Remove the thermostat cover using the correct tools and retain the fasteners.
- Note the orientation of the old thermostat before removing it.
- Clean the cover and mounting surfaces without damaging them.
- Install the thermostat and the supplied seal or gasket in the correct orientation.
- Reinstall the cover and tighten the fasteners to the engine manufacturer's specified torque.
- Run the engine according to the manufacturer's procedure and check for leaks or abnormal temperature behavior.
FAQ
What temperature does this thermostat open at?
This thermostat is specified to open at 50°C, equivalent to 122°F.
Is this an OEM Yamaha thermostat?
No. This is an aftermarket replacement intended for the listed Yamaha applications and reference numbers.
Does the package include a seal or gasket?
Yes. The applicable seal or thermostat-cover gasket is included, as specified by the corresponding application record.
Will this fit every Yamaha outboard from 3 to 250 HP?
No. The horsepower range summarizes multiple specific application groups. Confirm the exact model, stroke type, and original thermostat reference before purchasing.
Can I install it myself?
Installation may be suitable for an experienced DIY mechanic, but follow the engine manufacturer's service procedure and torque specifications. Professional installation is recommended if you are unsure of the correct application or installation method.
Safety and Compatibility Information
- Verify the complete engine model and stroke type before ordering.
- Do not use horsepower alone to determine compatibility.
- Compare the original thermostat and seal or gasket with the replacement before installation.
- Stop operation and inspect the cooling system if the engine overheats or shows abnormal temperature behavior.
About Sea Sierra
Sea Sierra supplies aftermarket marine replacement parts for maintenance and repair applications. Product fitment is based on the specific model and reference information provided above.
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