18-3544 Thermostat Assembly for Johnson Evinrude | JLM Marine

Thermostat Assembly for Johnson Evinrude 90-175 HP – 18-3544

This thermostat assembly is designed to fit Johnson/Evinrude outboard engines from 90 to 175 HP, including both carbureted and Ficht fuel-injected models with 60-degree V4 and V6 configurations. It is also compatible with select Mercury applications. Engineered for reliable temperature regulation, this component helps maintain optimal operating temperatures and prevent engine overheating.

Direct replacement for OEM part numbers: 0435491, 18-3544, 765559, 8M6010305, 8M0175329. Also cross-references with Sierra 18-3544 and GLM 13130.

• Fits Johnson/Evinrude 4-cylinder and 6-cylinder engines (3.600 bore, 60-degree)
• Compatible with carbureted and Ficht fuel-injected models from 1993–2006
• OEM-spec replacement for reliable thermal management

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 Serial Number Guide.

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.

Technical Specifications

Package Contents

• 1 × Thermostat Assembly (18-3544)

Installation Guide

1. Ensure the engine is completely cool and disconnected from the battery before beginning work.
2. Locate the thermostat housing on your engine block; it is typically mounted near the cylinder head.
3. Drain the coolant from the cooling system to prevent spillage during removal.
4. Remove the bolts or fasteners securing the thermostat housing cover and carefully lift it off.
5. Extract the old thermostat assembly and inspect the housing and mating surfaces for corrosion or debris.
6. Clean all gasket surfaces thoroughly using a gasket scraper and ensure no old gasket material remains.
7. Position the new thermostat assembly into the housing, ensuring proper orientation (spring side typically faces into the engine).
8. Install a new gasket or apply marine-grade sealant as specified by your engine's service manual.
9. Reinstall the thermostat housing cover and torque the bolts to manufacturer specifications in a crisscross pattern.
10. Refill the cooling system with the correct type and quantity of coolant or fresh water, depending on your system.
11. Reconnect the battery, start the engine, and check for leaks around the housing.
12. Allow the engine to reach operating temperature and verify that the thermostat opens properly and the cooling system functions correctly.

Troubleshooting & FAQ

Q: How do I confirm this thermostat fits my engine?
A: Check the Compatible Engine Models table above for your engine's HP, cylinder configuration, and year range. Cross-reference your original OEM part number (0435491, 765559, 8M6010305, or 8M0175329) with the Part Number Cross-Reference table to ensure compatibility.

Q: How often should I replace my thermostat?
A: Thermostats should be inspected annually and replaced every 2–3 years or sooner if you experience overheating, erratic temperature readings, or poor engine performance. Salt water and high-hour operation may require more frequent replacement.

Q: What are the signs of a failing thermostat?
A: Common symptoms include engine overheating, running colder than normal, inconsistent temperature gauge readings, or coolant leaks around the housing. If you notice any of these issues, inspect and replace the thermostat as needed.

Q: Can I use this thermostat on both carbureted and Ficht engines?
A: Yes, this thermostat assembly is designed to fit both carbureted and Ficht fuel-injected Johnson/Evinrude models within the specified HP and year ranges listed in the compatibility table.

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.