Thermostat for Yamaha F100D/F100L/F100X Four-Stroke Outboards, 55°C, Replaces 6D9-12411-00
Thermostat for Yamaha F100D/F100L/F100X Four-Stroke Outboards, 55°C, Replaces 6D9-12411-00 is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
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Thermostat for Yamaha F100D/F100L/F100X Four-Stroke Outboards, 55°C...
Thermostat for Yamaha F100D/F100L/F100X Four-Stroke Outboards, 55°C, Replaces 6D9-12411-00 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket replacement thermostat is designed for Yamaha F100D, F100L, and F100X four-stroke outboard engines. It is specified for a 55°C (131°F) operating temperature and replaces Yamaha OEM part number 6D9-12411-00.
The thermostat helps regulate engine temperature by controlling coolant flow through the outboard's cooling system. Replacing a thermostat that is sticking, damaged, or no longer maintaining the correct operating temperature can help restore proper cooling-system operation.
- Replacement thermostat for selected Yamaha four-stroke outboards.
- 55°C (131°F) temperature specification.
- Supplied as one thermostat.
- Confirm the engine model and original part number before ordering.
Part Number Matrix
Use the verified reference below when comparing the replacement with the part removed from your engine.
| Brand | Part Number | Reference Type |
|---|---|---|
| Yamaha | 6D9-12411-00 | OEM reference |
Engine & Model Compatibility
Fitment is limited to the Yamaha four-stroke models and conditions listed below. The company fitment record specifies model-year coverage for the F100D; no model-year range is stated for the F100L or F100X.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Yamaha | F100D | 100 | 4-Stroke | 2005–2018 | 6D9-12411-00 |
| Yamaha | F100L | 100 | 4-Stroke | Not specified | 6D9-12411-00 |
| Yamaha | F100X | 100 | 4-Stroke | Not specified | 6D9-12411-00 |
Technical Specs
- Product Type
- Marine engine thermostat
- Application
- Yamaha four-stroke outboard cooling system
- Installation
- Replacement installation in the thermostat housing
- Operating Temperature
- 55°C (131°F)
- Reference OEM Part
- 6D9-12411-00
What’s in the Box
- 1 x thermostat
A thermostat housing gasket or seal is not specified as included. Inspect the existing seal during disassembly and replace it if required for a proper seal.
Installation Notes
- Make sure the engine is stopped, cool, and safely supported before beginning work.
- Disconnect the battery if required by the engine manufacturer's service procedure.
- Locate the thermostat housing and place a suitable drain pan beneath the work area.
- Remove the housing cover carefully and note the orientation of the original thermostat.
- Remove the old thermostat and clean the mating surfaces, taking care not to damage the housing.
- Install the replacement thermostat in the same orientation as the original part.
- Inspect the housing gasket or seal and replace it if damaged or if the service procedure calls for replacement.
- Reinstall the housing cover and tighten the fasteners to the manufacturer's specified torque.
- Restore the cooling-water supply, start the engine, and check for leaks and proper water flow before normal operation.
Follow the Yamaha service manual for your exact engine when performing installation, torque, bleeding, and testing procedures.
Troubleshooting & FAQ
How do I know if my thermostat may have failed?
Possible symptoms include overheating, an engine that runs cooler or hotter than expected, unstable temperature behavior, or poor cooling-system performance. Test the thermostat and cooling system according to the service manual for your engine.
Is a new gasket included?
No gasket is specified as included with this product. Inspect the thermostat housing gasket or seal during installation and replace it when necessary.
At what temperature is this thermostat specified?
The company specification for this thermostat is 55°C (131°F).
Which Yamaha engines does this thermostat fit?
The listed fitment is for Yamaha F100D, F100L, and F100X four-stroke outboards. The F100D coverage is listed as 2005–2018; a year range is not specified for the F100L and F100X, so verify the model label and original part number before purchase.
Is this an OEM thermostat?
This listing is for an aftermarket replacement, not a Yamaha-branded OEM component. It is identified as a replacement for Yamaha part number 6D9-12411-00.
How quickly is the order shipped?
Typical transit is 5–15 days for standard worldwide shipping. Available shipping methods and delivery estimates are shown at checkout.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal use. Returns are accepted within the applicable standard return window when the item is unused and in its original condition. Contact support for current policy and return instructions.
Safety & Important Info
- Verify the engine model, year where applicable, original thermostat, and OEM reference before ordering.
- Do not operate the outboard if it overheats, leaks, or does not show proper cooling-water flow.
- This is an aftermarket replacement, not a Yamaha-branded OEM component.
- Professional installation is recommended when the correct service procedure or torque specification is unfamiliar.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for dependable service in real-world conditions.
- Fast Global Fulfillment — Standard delivery is available to most regions, with shipping options shown at checkout.
- Manufacturer-Direct Value — We aim to provide practical replacement parts at competitive prices.
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