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 for Johnson/Evinrude V4 Crossflow outboard engines ranging from 65 HP to 140 HP, covering model years from 1978 to 1995. It ensures proper engine temperature regulation for reliable performance across a wide range of applications including jet models and commercial units.

This kit directly replaces OEM part number 18-3673, providing an exact-fit aftermarket solution for maintenance and repair needs.

• Designed specifically for V4 Crossflow engine architecture
• Includes complete thermostat assembly components
• Ensures optimal operating temperature for engine longevity

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

This thermostat kit includes all necessary components for a complete installation:

• Thermostat assembly
• Gaskets and seals

Note: Verify all components against your original parts before installation.

Installation Guide

1. Preparation: Ensure the engine is completely cool and disconnect the battery. Gather necessary tools including screwdrivers, wrenches, and a gasket scraper.
2. Access the Thermostat Housing: Locate the thermostat housing on your V4 Crossflow engine, typically on the cylinder head. Remove any cowling or components blocking access.
3. Drain Coolant (if applicable): Place a drain pan beneath the engine and carefully drain coolant to prevent spills.
4. Remove Old Thermostat: Unbolt the thermostat housing cover and carefully remove the old thermostat. Note the orientation for proper installation of the new unit.
5. Clean Mating Surfaces: Thoroughly clean all gasket surfaces on both the housing and cover using a gasket scraper. Ensure no old gasket material or debris remains.
6. Install New Gasket: Position the new gasket from the kit onto the thermostat housing, ensuring proper alignment with bolt holes.
7. Install New Thermostat: Place the new thermostat into the housing in the same orientation as the original. Ensure it seats properly in the recess.
8. Reinstall Housing Cover: Carefully position the cover over the thermostat and gasket. Hand-tighten bolts first to ensure proper alignment.
9. Torque Bolts: Tighten housing bolts in a cross-pattern to manufacturer's specifications to ensure even pressure and prevent leaks.
10. Refill Coolant (if applicable): Refill the cooling system with fresh coolant to the proper level. Check for any immediate leaks around the housing.
11. Test Run: Reconnect the battery and start the engine. Allow it to reach operating temperature while monitoring for leaks and proper thermostat operation.
12. Final Inspection: After the engine cools, recheck all connections and coolant level. Verify no leaks are present before returning to normal operation.

Troubleshooting & FAQ

Q: How do I confirm this thermostat kit fits my specific Johnson/Evinrude engine?
A: Cross-reference your engine's horsepower, year, and model designation with the compatibility table above. Ensure your engine is a V4 Crossflow design and not a 60° model if you have a 90 HP or 115 HP engine. Verify the OEM part number 18-3673 matches your engine's service manual or existing thermostat.

Q: How often should I replace my outboard thermostat?
A: Thermostats should be inspected annually and replaced every 2-3 years or sooner if you experience overheating, inconsistent operating temperatures, or corrosion. Saltwater use accelerates wear and may require more frequent replacement.

Q: What are the signs of a failing thermostat in my outboard?
A: Common symptoms include engine overheating, running too cool (below normal operating temperature), steam from the engine, reduced performance, or the overheat alarm sounding. If the thermostat sticks closed, the engine will overheat; if stuck open, it won't reach proper operating temperature.

Q: Can I install this thermostat kit myself or do I need a professional?
A: Installation is straightforward for those with basic mechanical skills and tools. However, proper torque specifications, gasket sealing, and cooling system refilling are critical. If you're unfamiliar with outboard cooling systems, professional installation is recommended to avoid damage.

Q: Is this an OEM part or an aftermarket replacement?
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.