Thermostat – Fits Johnson/Evinrude 6-250 HP V4/V6 Outboard Motors (Replaces 5005440, 434841)
Thermostat – Fits Johnson/Evinrude 6-250 HP V4/V6 Outboard Motors (Replaces 5005440, 434841) is backordered and will ship as soon as it is back in stock.
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Thermostat – Fits Johnson/Evinrude 6-250 HP V4/V6 Outboard Motors (...
Thermostat – Fits Johnson/Evinrude 6-250 HP V4/V6 Outboard Motors (Replaces 5005440, 434841) is backordered and will ship as soon as it is back in stock.
Product Details
This high-quality Marine Thermostat – Fits Johnson Evinrude 6-250 HP V4/V6 Outboard Motors (Replaces 5005440, 434841) is designed for a wide range of Johnson/Evinrude 2-Stroke V4/V6 engines (6-250 HP, 1973–2006) and select 4-Stroke models (9.9-15 HP, 1994–2001). Its 143°F (62°C) temperature rating ensures your engine's cooling system operates correctly for optimal performance and longevity.
This thermostat is a direct replacement for Johnson/Evinrude part numbers 5005440, 8330720, 378065, 393659, 434841, 437414, and 508626, as well as Mercury 62981, 66850, 75692, 75692B and Sierra 18-3543 or 18-3553.
- Engineered as a direct-fit replacement for straightforward installation.
- Opens at 143°F (62°C) to maintain correct engine operating temperature.
- Manufactured to meet or exceed OEM specifications for reliable performance.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Johnson/Evinrude | 5005440 |
| Johnson/Evinrude | 8330720 |
| Johnson/Evinrude | 378065 |
| Johnson/Evinrude | 393659 |
| Johnson/Evinrude | 434841 |
| Johnson/Evinrude | 437414 |
| Johnson/Evinrude | 508626 |
| Mercury | 62981 |
| Mercury | 66850 |
| Mercury | 75692 |
| Mercury | 75692B |
| Sierra | 18-3543 |
| Sierra | 18-3553 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Johnson/Evinrude motors, this thermostat fits a broad range of 2-stroke and 4-stroke models produced between 1973 and 2006.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Johnson/Evinrude | Four-Stroke | 9.9 | 4-Stroke | 1994–2001 | 5005440, 434841 |
| Johnson/Evinrude | Four-Stroke | 15 | 4-Stroke | 1994–2001 | 5005440, 434841 |
| Johnson/Evinrude | V4 Models | 40–250 | 2-Stroke | 1973–2006 | 5005440, 434841 |
| Johnson/Evinrude | V6 Models | 60–250 | 2-Stroke | 1973–2006 | 5005440, 434841 |
| Johnson/Evinrude | Various Models | 6–55 | 2-Stroke | 1973–2006 | 5005440, 434841 |
For Mercury/Mariner motors, the part serves as a cross-reference. Please verify your specific application before ordering.
| Brand | OEM Part No. | Notes |
|---|---|---|
| Mercury | 62981, 66850, 75692, 75692B | Cross-reference application only |
Technical Specs
- Product Type
- Marine Outboard Thermostat
- Installation
- Direct replacement
- Temperature Rating
- 143°F (62°C)
- Fuel Type
- Gasoline
- Housing Material
- Brass/Stainless Steel (varies by manufacturer)
- Operating Temperature
- 62°C (143°F) opening temperature
- Warranty
- Varies by manufacturer (typically 1-year limited warranty)
- Other Technical Attributes
- Manufactured to OEM specifications
What’s in the Box
- 1 x Thermostat (5005440)
- 2 x Thermostat Seals (0329319) (Note: Seals are not included by all manufacturers)
Installation Notes
- Disconnect the battery and ensure the engine is cool to the touch.
- Locate the thermostat housing on the engine block or cylinder head.
- Place a drain pan under the housing and slowly loosen the bolts to drain the coolant.
- Remove the housing cover, old thermostat, and any existing gasket or seal material.
- Clean the mating surfaces of the housing and cover thoroughly.
- Install the new thermostat, ensuring it is oriented correctly.
- Place the new seal or gasket onto the housing.
- Reinstall the housing cover and tighten the bolts to the manufacturer's specified torque.
- Refill the cooling system with the appropriate coolant.
- Reconnect the battery, start the engine, and check for leaks and proper temperature gauge operation.
Troubleshooting & FAQ
How do I know if my thermostat is failing?
Common signs include engine overheating (gauge reads high), or the engine not reaching operating temperature (gauge reads low). You may also notice poor performance, increased fuel consumption, or steam from the engine.
Is 143°F the correct temperature for my engine?
This 143°F (62°C) thermostat is the specified temperature for the listed Johnson/Evinrude and cross-referenced models. Using the correct temperature is critical for engine performance and preventing carbon buildup.
Can I test my old thermostat?
Yes. Suspend the thermostat in a pot of water with a thermometer. Heat the water and observe the temperature at which it starts to open. If it fails to open at or near its rated temperature (143°F), it should be replaced.
Does this thermostat fit both 2-stroke and 4-stroke engines?
Yes, it is designed for a wide range of 2-Stroke V4/V6 engines from 1973-2006 and specific 4-Stroke 9.9/15 HP models from 1994–2001. Always verify your exact model and year in the compatibility chart.
Do I need to replace the seals at the same time?
It is highly recommended to replace the thermostat seals or gaskets whenever the thermostat is replaced to ensure a leak-proof seal. While this kit includes seals, availability may vary by supplier, so confirm contents upon purchase.
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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