Thermostat 50°C – Fits Yamaha 2-Stroke 3HP-250HP Outboards (Replaces 6E5-12411, 688-12411-10, 6H3-12411)
Thermostat 50°C – Fits Yamaha 2-Stroke 3HP-250HP Outboards (Replaces 6E5-12411, 688-12411-10, 6H3-12411) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Thermostat 50°C – Fits Yamaha 2-Stroke 3HP-250HP Outboards (Replace...
Thermostat 50°C – Fits Yamaha 2-Stroke 3HP-250HP Outboards (Replaces 6E5-12411, 688-12411-10, 6H3-12411) is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket Thermostat 50°C – Fits Yamaha 2-Stroke 3HP-250HP Outboards (Replaces 6E5-12411, 688-12411-10, 6H3-12411) is designed for a broad range of Yamaha 2-Stroke engines from 3 HP to 250 HP, covering models from 1984 to 2004. It maintains an operating temperature of 50°C (122°F) to ensure optimal engine performance. It is also compatible with select Parsun & Makara Marine 2-Stroke models, though confirmation with manufacturer specifications is recommended.
This component is a direct interchange for Yamaha OEM part numbers 688-12411-10-00, 688-12411-11-00, 6H3-12411-11-00, 6E5-12411-30-00, 6E5-12411-20-00, 6E5-12411-10-00, 6E5-12411-02, and 6E5-12411-00, as well as aftermarket reference T15-04000010.
- Engineered for direct OEM-fit installation.
- Maintains a consistent 50°C (122°F) operating temperature.
- Manufactured to OEM specifications for reliability.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Yamaha | 688-12411-10-00 |
| Yamaha | 688-12411-11-00 |
| Yamaha | 6H3-12411-11-00 |
| Yamaha | 6E5-12411-30-00 |
| Yamaha | 6E5-12411-20-00 |
| Yamaha | 6E5-12411-10-00 |
| Yamaha | 6E5-12411-02 |
| Yamaha | 6E5-12411-00 |
| Yamaha | 6E5-12411 |
| Aftermarket | T15-04000010 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Yamaha engines, this thermostat fits a wide variety of 2-stroke models produced between 1984 and 2004. Please verify your specific model and year against the list.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Yamaha | 3A, 4A | 3–4 HP | 2-Stroke | 6E5-12411-02 | |
| Yamaha | 5C, 6C/D/J, 8C/J | 5–8 HP | 2-Stroke | 6E5-12411-02 | |
| Yamaha | 8MSH-0405/0406/0407/0608, 8MSHD-2005 | 8 HP | 2-Stroke | 6E5-12411-02 | |
| Yamaha | 9.9B/C (Enduro), 15B (Enduro) | 9.9–15 HP | 2-Stroke | 6E5-12411-02 | |
| Yamaha | 20D | 20 HP | 2-Stroke | Up to 1993 | 6E5-12411-02 |
| Yamaha | 25A/B/J/N/V (Enduro and later models) | 25 HP | 2-Stroke | 1993–2001+ | 6E5-12411-02 |
| Yamaha | C30 | 30 HP | 2-Stroke | 1993+ | 6E5-12411-30 |
| Yamaha | 30D/G/H | 30 HP | 2-Stroke | 6E5-12411-30 | |
| Yamaha | 40X | 40 HP | 2-Stroke | 6E5-12411-30 | |
| Yamaha | 50G, 60F, 70B | 50–70 HP | 2-Stroke | 1984–2003 | 6H3-12411-10 |
| Yamaha | 115A/ETN | 115 HP | 2-Stroke | Up to 1985 | 6E5-12411-30 |
| Yamaha | 140A | 140 HP | 2-Stroke | Up to 1985 | 6E5-12411-30 |
| Yamaha | 150A/ETN | 150 HP | 2-Stroke | Up to 1985 | 6E5-12411-30 |
| Yamaha | 175A | 175 HP | 2-Stroke | Up to 1985 | 6E5-12411-30 |
| Yamaha | 200A/ETN | 200 HP | 2-Stroke | Up to 1985 | 6E5-12411-30 |
| Yamaha | 220A | 220 HP | 2-Stroke | Up to 1985 | 6E5-12411-30 |
| Yamaha | 250 | 250 HP | 2-Stroke | 1990–2004 | 6E5-12411-30 |
| Yamaha | 130B, 150F, Z150P/Q | 130–150 HP | 2-Stroke | 1994+ | 6E5-12411-30 |
| Yamaha | 175D, Z175G | 175 HP | 2-Stroke | 1994+ | 6E5-12411-30 |
| Yamaha | 200F/G, Z200N/P | 200 HP | 2-Stroke | 1994+ | 6E5-12411-30 |
| Yamaha | 225D/G | 225 HP | 2-Stroke | 1994+ | 6E5-12411-30 |
| Yamaha | 250A/B | 250 HP | 2-Stroke | 1994+ | 6E5-12411-30 |
For Parsun and Makara Marine engines, compatibility is generally cited for 2-stroke models from 3-250 HP. However, it is essential to confirm the part number with your engine's service manual or the manufacturer directly before ordering.
Technical Specs
- Product Type
- Thermostat
- Installation
- Direct replacement; OEM fit
- Fuel Type
- Gasoline
- Operating Temperature
- 50°C (122°F)
- Other Technical Attributes
- Manufactured to OEM specifications
What’s in the Box
- 1 x Thermostat (Replaces 6E5-12411 series, 688-12411 series)
Installation Notes
- Ensure the engine is completely cool and disconnected from the power source.
- Locate the thermostat housing on the engine block, referring to your owner's manual.
- Place a drain pan beneath the housing to catch any residual coolant.
- Carefully remove the bolts securing the housing cover. Note their length and position if they differ.
- Gently pry the cover open. If it is stuck, tap it lightly with a rubber mallet; do not force it with a screwdriver.
- Remove the old thermostat and gasket. Take note of the thermostat's orientation.
- Clean both the housing and cover mating surfaces thoroughly, removing all old gasket material and corrosion.
- Install the new thermostat in the correct orientation. Ensure it is properly seated.
- Install the new gasket, applying a sealant if recommended by your service manual.
- Reattach the housing cover and tighten the bolts in a crisscross pattern to the manufacturer's specified torque.
- Refill the cooling system, check for leaks, and run the engine to verify proper operation and temperature.
Troubleshooting & FAQ
How do I know if my thermostat is failing?
Common signs of a bad thermostat include engine overheating, temperature gauge fluctuations, or the engine not reaching its normal operating temperature. You may also notice coolant leaks around the thermostat housing.
Can I install a thermostat with a different temperature rating?
It is not recommended. This thermostat is rated for 50°C (122°F) to match OEM specifications for the listed engines. Using a different temperature can affect engine performance, fuel efficiency, and long-term health.
Is a new gasket required for installation?
Yes, it is always best practice to replace the thermostat housing gasket whenever the thermostat is replaced to ensure a proper seal and prevent coolant leaks. A gasket is not included with this part and must be purchased separately.
What is the typical replacement interval for a marine thermostat?
While there is no fixed interval, it is good practice to inspect the thermostat during routine cooling system service (e.g., every 2-3 years or 200-300 hours). Many technicians recommend replacing it proactively to prevent failures that could lead to engine damage.
My Yamaha model is listed, but the year is not specified. Will this fit?
If your engine model is listed but the year range is missing, this part is generally compatible. However, we strongly advise cross-referencing your existing part number with the numbers provided in our Part Number Matrix to guarantee a perfect fit.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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