Yamaha Outboard Thermostat for F115B and F130A 4-Stroke – Replaces 6EK-12411-00, Sierra 18-3639
Yamaha Outboard Thermostat for F115B and F130A 4-Stroke – Replaces 6EK-12411-00, Sierra 18-3639 is backordered and will ship as soon as it is back in stock.
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Yamaha Outboard Thermostat for F115B and F130A 4-Stroke – Replaces ...
Yamaha Outboard Thermostat for F115B and F130A 4-Stroke – Replaces 6EK-12411-00, Sierra 18-3639 is backordered and will ship as soon as it is back in stock.
Product Details
This Yamaha outboard thermostat is an aftermarket replacement for select Yamaha 4-stroke outboards, including the F115B and F130A. It helps regulate engine operating temperature and is specified to begin opening at 122°F (50°C).
The thermostat replaces Yamaha part 6EK-12411-00 and corresponds to the full Yamaha reference 6EK-12411-00-00 shown in supporting catalog records. It is also listed as an aftermarket equivalent to Sierra 18-3639.
- Aftermarket replacement thermostat for Yamaha outboard cooling systems.
- Designed for select Yamaha F115B and F130A four-stroke applications.
- 122°F / 50°C opening temperature.
- Designed to meet the applicable OEM specification for the listed application.
Part Number Matrix
Use the references below when comparing your existing thermostat or service-manual parts list.
| Brand | Part Number | Reference Type |
|---|---|---|
| Yamaha | 6EK-12411-00 | OEM replacement reference |
| Yamaha | 6EK-12411-00-00 | Full catalog reference |
| Sierra | 18-3639 | Aftermarket equivalent reference |
Engine & Model Compatibility
This thermostat is listed for the following Yamaha four-stroke outboard applications. Always verify the complete engine model and serial number against your owner's or service manual before ordering.
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Yamaha | F115B | 115 | 4-Stroke | 6EK-12411-00 | Confirm the exact model and serial-number range. |
| Yamaha | F130A | 130 | 4-Stroke | 6EK-12411-00 | Confirm the exact model and serial-number range. |
Technical Specs
- Product Type
- Marine outboard engine thermostat
- Application
- Select Yamaha four-stroke outboards
- Listed Fitment
- Yamaha F115B and F130A
- Opening Temperature
- 122°F / 50°C
- Installation
- Replacement installation using the applicable service-manual procedure
- Product Type Classification
- Single thermostat; not a thermostat-and-seal kit
What’s in the Box
- 1 x Thermostat
Important: Hardware, gaskets, and seals are sold separately. Confirm that the required sealing components are available before beginning installation.
Installation Notes
- Turn the engine off and allow it to cool completely before servicing.
- Disconnect the battery or follow the safety procedure specified by the engine manufacturer.
- Locate the thermostat housing and remove the cover according to the service manual.
- Remove the old thermostat and inspect the housing, mating surfaces, and sealing components.
- Clean the mating surfaces without damaging the housing or cover.
- Install the replacement thermostat in the correct orientation.
- Install a suitable new seal or gasket if required; sealing components are not included with this thermostat.
- Reinstall the housing cover and tighten the fasteners to the manufacturer’s specified torque.
- Run the engine according to the service-manual procedure and check for leaks or abnormal temperature warnings.
Troubleshooting & FAQ
Which engines is this thermostat listed for?
The company fitment record lists Yamaha F115B and F130A four-stroke outboards. Supporting catalog records also show the corresponding thermostat reference in select F115 applications. Verify your complete model and serial number before purchase.
What is the thermostat opening temperature?
The listed opening temperature is 122°F (50°C).
Which part numbers does this thermostat replace?
The primary replacement reference is Yamaha 6EK-12411-00. The full catalog format 6EK-12411-00-00 and aftermarket reference Sierra 18-3639 may also appear during parts comparison.
Is this a complete thermostat kit?
No. This listing is for one thermostat only. Seals, gaskets, and installation hardware are sold separately.
What are common signs of a faulty thermostat?
Possible symptoms include overheating, an engine that runs cooler than expected, slow warm-up, inconsistent temperature behavior, or an engine temperature warning. Diagnose the cooling system and follow the service manual before replacing parts.
Can I install this thermostat myself?
Installation may be suitable for an experienced technician or confident DIY owner, but correct orientation, sealing, and fastener torque are important. Use the service manual for your exact engine or have the work performed by a qualified marine technician.
Is this an OEM thermostat?
This is an aftermarket replacement, not a Yamaha-branded OEM component. It is listed as a replacement for the specified Yamaha reference and as an equivalent to Sierra 18-3639.
Safety & Important Information
- Verify the complete engine model and serial number before ordering.
- Compare the replacement part with your original thermostat and confirm the required reference number.
- Do not operate the engine if the thermostat housing leaks or if temperature warnings continue after installation.
- Seals, gaskets, and hardware are sold separately and may be required for installation.
- This product is an aftermarket replacement, not an OEM component.
About Sea Sierra
- Marine Replacement Parts — We provide replacement components for common outboard service applications.
- Application-Focused Listings — Product references and fitment details are provided to help you compare the part with your engine.
- Service-Minded Support — Always use the manufacturer’s service information for final fitment and installation requirements.
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