Yamaha Outboard Engine Thermostat – Fits Yamaha 50HP, 60HP, 70HP (Replaces 6H3-12411-10-00, 6H3-12411-11-00)
Yamaha Outboard Engine Thermostat – Fits Yamaha 50HP, 60HP, 70HP (Replaces 6H3-12411-10-00, 6H3-12411-11-00) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Product Details
This is a replacement Yamaha Outboard Engine Thermostat designed to fit a wide range of Yamaha 2-stroke outboard engines, specifically 50 HP, 60 HP, and 70 HP models manufactured from 1984 to 2006. It regulates engine temperature by opening at 50°C (122°F) to ensure optimal performance and prevent overheating.
It serves as a direct interchange for Yamaha part numbers 6H3-12411-00-00, 6H3-12411-01-00, 6H3-12411-10-00, and 6H3-12411-11-00, as well as Sierra 18-3622 and other aftermarket equivalents.
- Designed for direct OEM-replacement installation.
- Regulates coolant flow at a fixed 50°C (122°F) temperature.
- Package includes the thermostat only; gasket is sold separately.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number | Superseded By |
|---|---|---|
| Yamaha | 6H3-12411-00-00 | 6H3-12411-11-00 |
| Yamaha | 6H3-12411-01-00 | 6H3-12411-11-00 |
| Yamaha | 6H3-12411-10-00 | 6H3-12411-11-00 |
| Yamaha | 6H3-12411-11-00 | |
| Sierra | 18-3622 | |
| Aftermarket | AM6H3-12411-10 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This thermostat is compatible with select Yamaha 2-stroke outboard engines from 50 HP to 70 HP manufactured between 1984 and 2006.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Yamaha | 50G/GEO/GETO | 50 | 2-Stroke | 1984–2006 | 6H3-12411-10-00 | Superseded by 6H3-12411-11-00 |
| Yamaha | 60F/FEDO/FEHT/FEO/FET/FETO | 60 | 2-Stroke | 1984–2006 | 6H3-12411-10-00 | Superseded by 6H3-12411-11-00 |
| Yamaha | 60TDR/TLR-B/TR-Z | 60 | 2-Stroke | 1984–2006 | 6H3-12411-10-00 | Superseded by 6H3-12411-11-00 |
| Yamaha | 70B/BEHDO/BEMO/BEO/BETO | 70 | 2-Stroke | 1984–2006 | 6H3-12411-10-00 | Superseded by 6H3-12411-11-00 |
| Yamaha | 70TDR/TR | 70 | 2-Stroke | 1984–2006 | 6H3-12411-10-00 | Superseded by 6H3-12411-11-00 |
Technical Specs
- Product Type
- Engine Thermostat
- Installation
- Direct OEM Replacement
- Fuel Type
- Gasoline
- Housing Color
- Metallic
- Dimensions
- Length: 6.5, Width: 6.5, Height: 5.5
- Operating Temperature
- 50°C (122°F)
- Other Technical Attributes
- Temperature Rating: 50°C (122°F)
What’s in the Box
- 1 x Thermostat (Replaces 6H3-12411-10-00 / 6H3-12411-11-00)
Installation Notes
- Ensure the engine is off and the battery is disconnected. Allow the engine to cool completely.
- Drain the engine coolant into a suitable container.
- Locate and remove the thermostat housing cover.
- Remove the old thermostat and discard it. Note its orientation.
- Thoroughly clean the mating surfaces of the housing and its cover.
- Install the new thermostat in the correct orientation.
- Install a new gasket (sold separately) and reinstall the housing cover, tightening bolts to the manufacturer's specified torque.
- Refill the cooling system with the recommended coolant.
- Reconnect the battery, start the engine, and check for any leaks around the housing as the engine warms up.
Troubleshooting & FAQ
How do I know if my thermostat has failed?
Common signs of a faulty thermostat include the engine overheating at high speeds, running too cold at idle or low speeds, erratic temperature gauge readings, increased fuel consumption, or visible coolant leaks around the thermostat housing.
Is a gasket included with this thermostat?
No, this listing is for the thermostat only. The gasket must be purchased separately to ensure a proper, leak-free seal upon installation.
What is the correct operating temperature?
This thermostat is rated to open at 50°C (122°F), which is the standard specification for the listed Yamaha engine models. Using the correct temperature thermostat is critical for engine performance and longevity.
How often should an outboard thermostat be replaced?
As a preventative maintenance measure, it's recommended to inspect your thermostat annually and replace it every 2-3 years, or according to the service interval in your owner's manual. Replacement is especially important if you frequently operate in saltwater.
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.
Payment & Security
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