Thermostat (143°F/62°C) – Fits Johnson/Evinrude 6-250 HP (Replaces 5005440, 378065, 393659)
Thermostat (143°F/62°C) – Fits Johnson/Evinrude 6-250 HP (Replaces 5005440, 378065, 393659) 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 (143°F/62°C) – Fits Johnson/Evinrude 6-250 HP (Replaces ...
Thermostat (143°F/62°C) – Fits Johnson/Evinrude 6-250 HP (Replaces 5005440, 378065, 393659) is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket Thermostat (143°F/62°C) – Fits Johnson/Evinrude 6-250 HP (Replaces 5005440, 378065, 393659) is designed for a broad range of Johnson/Evinrude outboard engines. It is engineered for E-TEC models from 40-250 HP, Cross V4 & V6 models from 6-55 HP, and 9.9-15 HP 4-Stroke models manufactured between 1994 and 2001.
It serves as a direct replacement for multiple OEM and aftermarket part numbers, including Johnson/Evinrude 5005440, 378065, 393659, 434841, Sierra 18-3543, GLM 13010, and Mallory 9-43019, ensuring wide compatibility.
- Installation: Installs as a direct replacement with no modifications required.
- Regulates Temperature: Opens at 143°F (62°C) to maintain optimal engine operating temperature.
- Durable Construction: Built from corrosion-resistant stainless steel and brass to withstand harsh marine environments.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Johnson/Evinrude | 5005440 |
| Johnson/Evinrude | 378065 |
| Johnson/Evinrude | 393659 |
| Johnson/Evinrude | 434841 |
| Johnson/Evinrude | 437414 |
| Johnson/Evinrude | 508626 |
| Sierra | 18-3543 |
| Sierra | 18-3553 |
| GLM | 13010 |
| Mallory | 9-43019 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This thermostat is designed for a wide range of Johnson and Evinrude 2-stroke and 4-stroke outboard motors, including E-TEC, Ficht, and various V4/V6 platforms.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Johnson/Evinrude | V4 & V6 Models | 40-250 | 2-Stroke | Various | 5005440 | E-TEC models |
| Johnson/Evinrude | Various Models | 6-55 | 2-Stroke | Various | 5005440 | Cross V4 & V6 models |
| Johnson/Evinrude | Various Models | 9.9-15 | 4-Stroke | 1994–2001 | 5005440 | |
| Johnson/Evinrude | E-TEC Models | 200-225 | 2-Stroke | 2004–2012 | 5005440 | 3.3 Liter |
| Johnson/Evinrude | E-TEC Models | 250 | 2-Stroke | 2007–2012 | 5005440 | 3.3 Liter |
| Johnson/Evinrude | E-TEC Models | 250 | 2-Stroke | 2008–2010 | 5005440 | 3.4 Liter |
| Johnson/Evinrude | E-TEC Models | 300 | 2-Stroke | 2008–2012 | 5005440 | 3.4 Liter |
| Johnson/Evinrude | Ficht Models | 200 | 2-Stroke | 2004 | 5005440 | 3.3 Liter |
| Johnson/Evinrude | Ficht Models | 225 | 2-Stroke | 2004–2005 | 5005440 | 3.3 Liter |
| Johnson/Evinrude | Ficht Models | 250 | 2-Stroke | 2004 | 5005440 | 3.3 Liter |
Technical Specs
- Product Type
- Outboard Engine Thermostat
- Installation
- Direct Replacement
- Opening Temperature
- 143°F (62°C)
- Housing Material
- Stainless Steel/Brass (varies by brand)
- Operating Temperature
- 62°C–93°C (143°F–200°F)
- Warranty
- Varies by manufacturer (typically 1 year)
What’s in the Box
- 1 x Thermostat (5005440)
- 2 x Thermostat Seals (0329319) - included with some kits
Installation Notes
- Disconnect the battery before beginning work.
- Allow the engine to cool completely and drain the cooling system.
- Locate the thermostat housing on the engine block or cylinder head.
- Remove the housing bolts, noting the orientation of the old thermostat before removing it.
- Clean the mating surfaces of the housing and engine block, removing any old gasket material.
- Install the new thermostat in the correct orientation, followed by the new seal or gasket.
- Re-install the housing cover and tighten the bolts to the manufacturer's specified torque.
- Refill the cooling system with the appropriate coolant, checking for any leaks.
- Reconnect the battery, start the engine, and let it reach operating temperature while monitoring for proper function and leaks.
Troubleshooting & FAQ
How do I know if my thermostat has failed?
Common signs include the engine overheating or running too cold (failing to reach normal operating temperature). Overheating can cause severe engine damage, while running too cool reduces fuel efficiency and accelerates engine wear.
What is the correct operating temperature for this thermostat?
This thermostat begins to open at 143°F (62°C) to allow coolant to circulate. The engine's normal operating temperature range with this part installed is typically 143°F–200°F (62°C–93°C).
Are gaskets or seals included in the package?
Package contents can vary. While some kits may include two thermostat seals (Part No. 0329319), others do not. Always check the contents upon receipt and be prepared to purchase seals separately if they are not included.
How often should I replace my outboard thermostat?
It is recommended to inspect the thermostat annually and replace it every 2-3 years as part of routine cooling system maintenance. Replacement is especially important for boats operated in saltwater environments.
My engine is listed as compatible, but the part looks different from my original. What should I do?
Do not install the part. Visually compare the new thermostat against your old one before installation. Manufacturing variations can occur. If you notice any differences, please contact our support team before proceeding.
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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