Marine Thermostat – Fits Johnson Evinrude 6-250 HP V4/V6 Outboard Motors (Replaces 5005440, 434841)

Marine Thermostat – Fits Johnson Evinrude 6-250 HP V4/V6 Outboard Motors (Replaces 5005440, 434841)

This high-quality aftermarket thermostat is designed for a wide range of Johnson and Evinrude outboard motors. It fits various 2-stroke V4/V6 engines (40–250 HP) from 1973–2006, other 2-stroke models (6–55 HP) from the same period, and 4-stroke models (9.9–15 HP) from 1994–2001. With a specified temperature rating of 143°F (62°C), it ensures your engine's cooling system operates correctly for optimal performance and longevity.

This component is a direct replacement for numerous original and aftermarket part numbers, including Johnson/Evinrude 5005440, 434841, 8330720, and Sierra 18-3543.

• Operating Temperature: Opens at 143°F (62°C) to regulate engine cooling.
• Installation: Designed for direct replacement of the original thermostat.
• Engine Compatibility: Fits a broad range of V4, V6, and other 2-stroke and 4-stroke Johnson/Evinrude models.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Johnson/Evinrude owners, here’s a guide to help you identify your engine’s serial/model: Johnson/Evinrude Serial Number Guide.

Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Johnson/Evinrude Models

Mercury/Mariner Models

Technical Specifications

Package Contents

• 1 x Thermostat (5005440)
• 2 x Thermostat Seals (0329319) (Note: Seals are not included by all manufacturers and may not be in your package)

Installation Guide

1. Safety First: Ensure the engine is completely cool and disconnected from the power source.
2. Locate Housing: Find the thermostat housing on the engine block or cylinder head.
3. Drain Coolant: Place a container underneath and partially drain the cooling system.
4. Remove Housing Cover: Loosen and remove the bolts securing the housing cover.
5. Extract Old Thermostat: Carefully remove the old thermostat and its seal or gasket. Note its orientation.
6. Clean Surfaces: Thoroughly clean the mating surfaces of the housing and cover, removing any old gasket material.
7. Install New Thermostat: Place the new thermostat into the housing in the correct orientation, followed by the new seal/gasket.
8. Secure Cover: Re-attach the housing cover and tighten the bolts to the manufacturer's specified torque.
9. Refill Coolant: Top off the cooling system with the appropriate coolant.
10. Check for Leaks: Start the engine, let it reach operating temperature, and carefully check for any leaks around the housing.

Troubleshooting & FAQ

How do I confirm this thermostat fits my engine? First, check the "Compatible Engine Models" tables on this page. We strongly recommend using our serial number guides for Johnson/Evinrude to verify your model and year. Cross-referencing your old part number with our "Part Number Cross-Reference" table is the best way to ensure an exact match.

What are the signs of a failing thermostat? Common symptoms include engine overheating (if stuck closed) or the engine failing to reach its proper operating temperature (if stuck open). An inaccurate temperature gauge reading can also indicate a faulty thermostat.

Does this kit include the necessary seals? The kit includes two thermostat seals (Part No. 0329319). However, please be aware that package contents can vary between manufacturers, and seals may not be included in all packages. Always check the contents upon arrival.

What is the operating temperature of this thermostat? This thermostat is rated to begin opening at 143°F (62°C), which is the standard OEM-specified temperature for the listed engine models to ensure proper cooling system function.

OEM vs. Aftermarket? This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

How fast do you ship and how much does it cost? We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

What is your warranty and return policy? This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.