Thermostat Kit with Hoses – Fits Johnson Evinrude V4 Crossflow 65-140HP (Replaces 18-3673, 340975, 340976)

Thermostat Kit with Hoses – Fits Johnson Evinrude V4 Crossflow 65-140HP (Replaces 18-3673, 340975, 340976)

This thermostat kit is designed for Johnson/Evinrude 65-140HP V4 Crossflow outboard engines manufactured between 1978 and 1995. It fits a wide range of models, including 65 & 80 Jet, 90 Jet, 85HP, 88HP, 90HP, 100HP, 110HP, 112HP, 115HP, and 140HP.

This kit is a direct replacement for Sierra 18-3673, GLM 13270, OMC 434841, and Johnson/Evinrude part numbers 340975, 340976.

• Complete Kit: Includes thermostat, gaskets, poppet valve components, and both starboard and port hoses.
• Direct Replacement: Engineered for a factory OEM fit on V4 Crossflow engines, ensuring a hassle-free installation.
• Optimal Temperature: The included thermostat is rated at 143°F (62°C) to maintain proper engine operating temperature.

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

• 1x Thermostat (Replaces 393659, 434841, 378065, 508626, 5005440)
• 1x Thermostat Gasket (Replaces 332369, 18-0977)
• 1x Poppet Relief Valve Gasket (Replaces 321932, 18-0675)
• 1x Poppet Relief Valve (Replaces 318395, 18-3564)
• 1x Grommet (Replaces 321692, 18-2391)
• 1x Valve Spring (Replaces 317245, 18-1243)
• 1x Starboard Hose (Replaces 340975, 18-70936, 321724)
• 1x Port Hose (Replaces 340976, 18-70937)

Installation Guide

1. Safety First: Disconnect the battery cables and ensure the engine is cool to the touch.
2. Drain Coolant: Place a container under the engine and drain the cooling system according to your service manual.
3. Access Housing: Locate and remove any components obstructing access to the thermostat and poppet valve housings.
4. Remove Old Components: Carefully detach the old starboard and port hoses. Unbolt the thermostat and poppet valve covers and remove the old valves, springs, gaskets, and thermostat.
5. Clean Surfaces: Thoroughly clean the gasket mating surfaces on the engine block and covers. Remove all old gasket material and corrosion.
6. Install New Poppet Valve: Insert the new spring, grommet, and poppet relief valve into the housing.
7. Install New Thermostat: Place the new thermostat and gasket into position. Ensure the thermostat is oriented correctly.
8. Secure Covers: Reinstall the thermostat and poppet valve covers with their new gaskets, tightening the bolts to the manufacturer's specified torque.
9. Attach New Hoses: Connect the new starboard and port hoses and secure them with clamps.
10. Refill and Test: Refill the cooling system with the appropriate coolant. Reconnect the battery, start the engine, and carefully check for any leaks around the new components.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my engine?
A: This kit is specifically for Johnson/Evinrude V4 Crossflow engines (65-140HP) from 1978–1995. The best way to confirm fitment is to check your engine model and year against the "Compatible Engine Models" table. Cross-referencing your existing part numbers with those listed (e.g., Sierra 18-3673, Johnson/Evinrude 340975, 340976) also ensures a perfect match.

Q: What are the symptoms of a failing thermostat or poppet valve?
A: Common signs of a bad thermostat include engine overheating at idle or low speeds, or the engine not reaching its proper operating temperature. A faulty poppet valve can cause overheating at high speeds. Coolant leaks around the housing are also a clear indicator that service is needed.

Q: What is the operating temperature of the included thermostat?
A: The thermostat in this kit is rated to open at 143°F (62°C). This ensures your engine warms up quickly and maintains the correct temperature for optimal performance, fuel efficiency, and longevity.

Q: Does this kit include everything needed for a complete replacement?
A: Yes, this is a comprehensive kit designed for a full service of the thermostat and poppet valve system. It includes the thermostat, all necessary gaskets, the poppet relief valve, spring, grommet, and the critical starboard and port hoses which often degrade over time.

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.