Thermostat – Fits Johnson Evinrude 6-250 HP V4/V6 (Replaces Johnson/Evinrude 5005440, 434841)
Thermostat – Fits Johnson Evinrude 6-250 HP V4/V6 (Replaces Johnson/Evinrude 5005440, 434841) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
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Thermostat – Fits Johnson Evinrude 6-250 HP V4/V6 (Replaces Johnson...
Thermostat – Fits Johnson Evinrude 6-250 HP V4/V6 (Replaces Johnson/Evinrude 5005440, 434841) is backordered and will ship as soon as it is back in stock.
Product Details
This replacement Thermostat – Fits Johnson Evinrude 6-250 HP V4/V6 Outboard Motors is designed for a broad range of 2-stroke and 4-stroke engines. It is engineered for Johnson/Evinrude 6–250 HP 2-Stroke V4/V6 models (1973–2006) and 9.9–15 HP 4-Stroke models (1994–2001). It also serves as a compatible replacement for select Mercury/Mariner and Yamaha outboards.
This part directly interchanges with Johnson/Evinrude 5005440 / 434841, Mercury 75692, Yamaha 6F5-12411-03-00, Sierra 18-3543, and GLM 13010, among other equivalents.
- Engineered as a direct-fit replacement for easy installation.
- Maintains optimal engine temperature with a 143°F (62°C) rating.
- Manufactured in an ISO 9002 certified facility to meet OEM specifications.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Johnson/Evinrude | 378065 / 393659 / 434841 / 437414 / 5005440 / 508626 |
| Mercury/Mariner | 62981 / 66850 / 75692 / 75692B |
| Yamaha | 6F5-12411-03-00 |
| Sierra | 18-3543 / 18-3553 |
| GLM | 13010 |
| AM | AM6F5-12411-02 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Johnson/Evinrude owners: This thermostat fits a wide variety of V4, V6, and other 2-stroke motors from 1973–2006, plus specific 4-stroke models. Verify your OEM part number for a perfect match.
For Mercury/Mariner owners: Compatibility is based on part number matching. Please cross-reference your existing part number with those listed in our Part Number Matrix.
For Yamaha owners: Primarily fits models specifying OEM part number 6F5-12411-03-00. Always verify before ordering.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. |
|---|---|---|---|---|---|
| Johnson/Evinrude | Four-Stroke | 9.9 | 4-Stroke | 1994–2001 | 378065, 393659, 434841, 437414, 5005440, 508626 |
| Johnson/Evinrude | Four-Stroke | 15 | 4-Stroke | 1994–2001 | 378065, 393659, 434841, 437414, 5005440, 508626 |
| Johnson/Evinrude | V4 Models | 40–250 | 2-Stroke | 1973–2006 | 378065, 393659, 434841, 437414, 5005440, 508626 |
| Johnson/Evinrude | V6 Models | 60–250 | 2-Stroke | 1973–2006 | 378065, 393659, 434841, 437414, 5005440, 508626 |
| Johnson/Evinrude | Various Models | 6–55 | 2-Stroke | 1973–2006 | 378065, 393659, 434841, 437414, 5005440, 508626 |
Technical Specs
- Product Type
- Thermostat
- Installation
- Direct replacement
- Temperature Rating
- 143°F (62°C)
- Other Technical Attributes
- Manufactured to OEM specifications in an ISO9002 certified factory
What’s in the Box
- 1 x Thermostat (5005440)
Installation Notes
- Ensure the engine is off and cool. Disconnect the battery negative terminal for safety.
- Locate the thermostat housing on the engine block or cylinder head. Place a drain pan underneath if needed.
- Remove the bolts securing the housing cover. You may need to gently tap the cover to break the seal.
- Note the orientation of the old thermostat before removing it. The spring side usually faces the engine.
- Clean the mating surfaces of both the housing and its cover, removing all old gasket material.
- Install the new thermostat in the correct orientation. Place the new gasket into position.
- Re-install the housing cover and tighten the bolts evenly to the manufacturer's specified torque.
- Reconnect the battery, start the engine, and check for any coolant leaks around the housing as it warms up.
Troubleshooting & FAQ
How do I know if my outboard thermostat is failing?
Common signs include the engine overheating at low speeds but running cool at high speeds, or failing to reach its normal operating temperature (running too cool). Visible corrosion or a stuck-open/closed valve on the old thermostat are also clear indicators for replacement.
Why is the 143°F temperature rating important?
The temperature rating ensures your engine warms up quickly and maintains a consistent temperature for optimal performance, fuel efficiency, and reduced engine wear. Using the wrong temperature can lead to poor combustion or overheating.
Can I use this on a saltwater-cooled engine?
Yes, this thermostat is made with materials suitable for both freshwater and saltwater marine environments. Regular flushing of the cooling system is always recommended to prolong the life of all components.
Is a new gasket required for installation?
Yes, it is critical to use a new gasket whenever replacing a thermostat to ensure a proper seal and prevent coolant leaks. This package does not include a gasket unless specified in the "What's in the Box" section.
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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