Yamaha 2-Stroke Outboard Thermostat Kit, 115–250 HP – Replaces 6E5-12411-30-00
Yamaha 2-Stroke Outboard Thermostat Kit, 115–250 HP – Replaces 6E5-12411-30-00 is backordered and will ship as soon as it is back in stock.
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Yamaha 2-Stroke Outboard Thermostat Kit, 115–250 HP – Replaces 6E5-...
Yamaha 2-Stroke Outboard Thermostat Kit, 115–250 HP – Replaces 6E5-12411-30-00 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket thermostat kit is designed for selected Yamaha 2-stroke outboard engines from approximately 1991 through 2002, covering compatible 115–250 HP applications. It helps regulate engine operating temperature and supports reliable cooling-system performance when the original thermostat is worn, stuck, or no longer responding correctly.
The thermostat is listed as a replacement for Yamaha part number 6E5-12411-30-00 and is cross-referenced with Sierra 18-3540. Always compare the part number and engine model details before ordering.
- Aftermarket thermostat replacement for selected Yamaha 2-stroke outboards.
- Designed for direct replacement when the listed part number and application match.
- Kit includes one thermostat and one thermostat housing gasket.
- Thermostat opening rating: approximately 50°C / 122°F.
Part Number Matrix
Use the following references to compare your original part. Part-number matching should be confirmed together with the engine model, horsepower, stroke, year, and serial-number requirements.
| Brand | Part Number | Reference |
|---|---|---|
| Yamaha | 6E5-12411-30-00 | Replacement/OEM reference |
| Yamaha | 6E5-12411-20-00 | Additional catalog reference; verify application |
| Yamaha | 6E5-12411-10-00 | Additional catalog reference; verify application |
| Yamaha | 688-12411-10-00 | Additional catalog reference; verify application |
| Yamaha | 688-12411-11-00 | Additional catalog reference; verify application |
| Sierra | 18-3540 | Aftermarket thermostat reference |
Engine & Model Compatibility
The catalog application data for this thermostat identifies selected Yamaha 2-stroke engines in the ranges below. The year ranges are not universal for every variant, so confirm the complete model designation and the required OEM number before installation.
| Brand | Engine family or model | Rated HP | Stroke | Catalog year range | Reference |
|---|---|---|---|---|---|
| Yamaha | 115, C115, P115, S115 | 115 | 2-Stroke | 1991–2002, depending on variant | 6E5-12411-30-00 |
| Yamaha | 130, L130, S130 | 130 | 2-Stroke | 1991–2002, depending on variant | 6E5-12411-30-00 |
| Yamaha | 150, C150, L150, P150, S150, V150, Z150 | 150 | 2-Stroke | 1991–2002, depending on variant | 6E5-12411-30-00 |
| Yamaha | 175, P175, V175, Z175 | 175 | 2-Stroke | 1991–2002, depending on variant | 6E5-12411-30-00 |
| Yamaha | 200, L200, P200, S200, V200, Z200 | 200 | 2-Stroke | 1991–2002, depending on variant | 6E5-12411-30-00 |
| Yamaha | 225, V225 | 225 | 2-Stroke | 1991–1999, depending on variant | 6E5-12411-30-00 |
| Yamaha | LX225, LX250, SX225, SX250 | 225–250 | 2-Stroke | Selected 2003 catalog applications | 6E5-12411-30-00 |
Technical Specs
- Product Type
- Outboard engine thermostat kit
- Application
- Selected Yamaha 2-stroke outboard engines
- Horsepower Range
- 115–250 HP, depending on the exact model and year
- Installation
- Direct replacement when application and part number match
- Opening Temperature
- Approximately 50°C / 122°F
- Included Gasket
- Thermostat housing gasket
What’s in the Box
- 1 × Thermostat, replacing the listed 6E5-12411-30-00 application
- 1 × Thermostat housing gasket, cross-referenced with Yamaha 688-12414-A1-00
No separate thermostat seal is listed as an included component.
Installation Notes
- Disconnect the battery according to the engine manufacturer's safety procedure.
- Allow the engine to cool completely before opening the cooling system.
- Place a drain pan below the thermostat housing and remove the housing cover.
- Note the orientation of the original thermostat before removal.
- Clean the housing and cover mating surfaces, removing old gasket material without damaging the surfaces.
- Install the replacement thermostat in the original orientation, followed by the new housing gasket.
- Reinstall the cover and tighten the fasteners to the manufacturer's specified torque.
- Restore the cooling system as required, run the engine, and check for leaks and normal temperature operation.
Troubleshooting & FAQ
How do I know if my thermostat is failing?
Possible symptoms include overheating, an engine that runs too cool, unstable operating temperature, restricted cooling-water flow, or visible corrosion and deposits around the thermostat. Diagnose the complete cooling system before replacing the part.
Is this the correct temperature rating for my engine?
This thermostat is listed with an opening temperature of approximately 50°C / 122°F. Verify that this temperature and the replacement part number match your engine service information before installation.
My exact model is not listed. Will it still fit?
Do not assume fitment from horsepower alone. Compare the complete engine model, year, serial range, original thermostat, and required OEM part number with the information above.
Is this an OEM thermostat?
No. This is an aftermarket replacement kit intended to match the listed application and reference numbers. Yamaha and other brand names and part numbers are used only to identify compatibility.
Does the kit include a seal?
The documented package contents include one thermostat and one thermostat housing gasket. A separate thermostat seal is not listed as included.
When should the thermostat be replaced?
Inspect the thermostat during cooling-system service and replace it if it sticks, fails a temperature test, shows corrosion, or does not meet the engine manufacturer's specifications. Follow the maintenance schedule for your specific engine.
Shipping speed and cost
Shipping options, delivery estimates, and cost are shown at checkout based on the destination and service selected.
Warranty and returns
Warranty and return eligibility are governed by the current store policies. Contact support with your order details if you need assistance.
Safety & Important Information
- Confirm the exact part number and application before ordering.
- Never open the thermostat housing while the engine or coolant is hot.
- Use the manufacturer's torque, gasket, cooling-system, and installation procedures.
- Professional installation is recommended if you are not familiar with outboard cooling-system service.
- This is an aftermarket replacement, not an OEM component.
About Sea Sierra
- Marine Replacement Parts — Practical aftermarket parts for routine service and repair.
- Application-Focused Listings — Product references and compatibility information are provided to help you verify fitment.
- Customer Support — Contact support with your engine details and original part information when you need help confirming an application.
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