Thermostat Kit – Fits Johnson/Evinrude V4 Crossflow 65-140 HP (Replaces 434841, 18-3673)

Thermostat Kit – Fits Johnson/Evinrude V4 Crossflow 65-140 HP (Replaces 434841, 18-3673)

This thermostat kit is designed for Johnson/Evinrude 65-140 HP V4 Crossflow outboard engines, covering models from 1978 to 1995. It is a direct replacement for multiple OEM and aftermarket parts, ensuring a precise fit for a wide range of applications, including 80 HP Jet and various commercial models.

This kit provides a comprehensive solution for servicing dual thermostat systems, restoring proper engine operating temperature and performance. It is designed to replace Sierra 18-3673, GLM 13270, and a range of OMC part numbers including 434841 and 5005440.

• Includes two 143°F (62°C) stainless steel thermostats for dual systems.
• Engineered as a direct replacement for easy installation.
• Complete kit with all necessary seals, springs, and poppet valves.

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.

Technical Specifications

Package Contents

• 2 x Stainless thermostats (143°F)
• 2 x Thermostat base seals
• 2 x Poppet valves
• 2 x Poppet seat seals
• 2 x Poppet springs
• 2 x Gaskets

Installation Guide

1. Ensure the engine is off and cool. Disconnect the negative battery cable for safety.
2. Locate the thermostat housings on the engine cylinder heads.
3. Place a drain pan under the engine and carefully remove the housing covers and gaskets.
4. Note the orientation of the old thermostats and poppet assemblies before removing them.
5. Clean all mating surfaces of any old gasket material or corrosion.
6. Install the new poppet valves, springs, and seals into the housings.
7. Install the new thermostats, ensuring they are seated correctly, followed by the new gaskets.
8. Securely fasten the housing covers.
9. Reconnect the battery cable, start the engine, and check for any leaks around the housings.
10. Monitor the engine temperature to ensure it operates within the normal range.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my V4 engine?

A: This kit is specifically for V4 Crossflow models. It will not fit 60° V6/V8 or Looper engines. Please check your engine model and year against the compatibility table. Cross-referencing your existing part number with the numbers provided (e.g., Sierra 18-3673, OMC 434841) is the most reliable method.

Q: Why does this kit include two of everything?

A: The Johnson/Evinrude V4 Crossflow engines covered by this kit use a dual thermostat system, with one thermostat assembly per cylinder bank. This kit includes all necessary components to service both sides.

Q: What are the common signs of a failing thermostat?

A: A thermostat stuck open will cause the engine to run too cool, leading to poor fuel efficiency and carbon buildup. A thermostat stuck closed will cause the engine to overheat, which can result in serious damage. An erratic temperature gauge is also a common indicator.

Q: OEM vs. Aftermarket?

A: 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.

Q: How fast do you ship and how much does it cost?

A: 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.

Q: What is your warranty and return policy?

A: 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.