18-3673 Thermostat Kit for Johnson Evinrude V4 Crossflow | JLM Marine

18-3673 Thermostat Kit for Johnson Evinrude V4 Crossflow | JLM Marine

This thermostat kit is engineered to fit Johnson/Evinrude V4 Crossflow outboard engines ranging from 65 HP to 140 HP, covering model years from the late 1970s through the mid-1990s. It ensures reliable temperature regulation for optimal engine performance across a wide range of V4 configurations, including Jet models and commercial applications.

This kit directly replaces OEM part number 18-3673, providing an exact-fit aftermarket solution for your engine's cooling system. Designed to match factory specifications, it delivers dependable service for both recreational and commercial marine applications.

• Fits Johnson/Evinrude V4 Crossflow engines from 65 HP to 140 HP
• Direct replacement for OEM part number 18-3673
• Ensures proper engine temperature regulation and cooling system performance

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

• Thermostat Kit (Part# 18-3673)

Installation Guide

1. Allow the engine to cool completely before beginning work. Disconnect the battery to prevent accidental starts.
2. Drain the cooling system and remove the thermostat housing cover by loosening the retaining bolts. Keep track of all fasteners and gaskets.
3. Remove the old thermostat and clean the mating surfaces thoroughly, removing all old gasket material and debris.
4. Install the new thermostat in the correct orientation as indicated by the arrow or spring direction. Ensure it seats properly in the housing recess.
5. Apply a thin layer of gasket sealant if recommended by your engine manual, then position a new gasket on the housing.
6. Reinstall the thermostat cover and torque the bolts to manufacturer specifications in a criss-cross pattern.
7. Refill the cooling system with fresh coolant or water as appropriate for your engine type. Check for proper fluid level.
8. Reconnect the battery and start the engine, allowing it to reach operating temperature. Monitor for leaks around the thermostat housing.
9. Verify that the thermostat opens properly by checking coolant flow and engine temperature stability.

Troubleshooting & FAQ

Q: How do I confirm this thermostat kit fits my engine?
A: Cross-reference your engine's model, horsepower, and year with the compatibility table above. Verify your engine is a V4 Crossflow design and not a 60° model if you have a 90 HP or 115 HP unit, as those variants are excluded.

Q: How often should I replace my thermostat?
A: Thermostats should be inspected annually and replaced every 2-3 years or whenever you notice overheating, erratic temperature readings, or corrosion. Regular replacement prevents cooling system failures.

Q: What are the signs of a failing thermostat?
A: Common symptoms include engine overheating, running too cool, inconsistent temperature gauge readings, poor fuel economy, or excessive steam from the exhaust. If you experience any of these, inspect and replace the thermostat promptly.

Q: Can I install this kit myself or do I need a mechanic?
A: Basic mechanical skills and tools are sufficient for most DIY installations. However, if you're unfamiliar with marine cooling systems or lack the proper torque specifications, professional installation is recommended to avoid leaks or damage.

Q: What's the difference between OEM and aftermarket thermostats?
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.