Thermostat – Fits Mercury/Mariner F40/F50/F60 EFI 4-Cylinder 4-Stroke Outboards (Replaces 8M0117413, 8M0168892)

Thermostat – Fits Mercury/Mariner F40/F50/F60 EFI 4-Cylinder 4-Stroke Outboards (Replaces 8M0117413, 8M0168892)

This thermostat is a direct-fit replacement for Mercury/Mariner 40–60 HP, 4-cylinder, 4-stroke EFI outboard engines (serial number 1C050252 and up). It is engineered to maintain the correct engine operating temperature for optimal performance and fuel efficiency.

It serves as an aftermarket replacement for Mercury OEM parts 8M0117413 and 8M0168892, as well as Sierra part 18-3640 and OMAX part 8M0117413.

• Temperature Rating: 122°F / 50°C
• Installation Type: Direct replacement in thermostat housing
• Construction: Built with durable, corrosion-resistant materials for marine environments

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 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 x 122°F/50°C Outboard Thermostat (Replaces 8M0117413/8M0168892)

Installation Guide

1. Ensure the engine is completely cool and disconnect the negative battery terminal for safety.
2. Locate the thermostat housing on the engine. Refer to your owner's manual if needed.
3. Place a drain pan under the housing to catch any coolant that spills.
4. Carefully unbolt and remove the thermostat housing cover.
5. Note the orientation of the old thermostat before removing it from the housing.
6. Thoroughly clean the mating surfaces of the housing and its cover, removing all old gasket material.
7. Install the new thermostat, making sure it is oriented correctly.
8. Position the new gasket and securely reinstall the housing cover, tightening the bolts to the manufacturer's recommended torque.
9. Reconnect any hoses, top off the engine coolant, and check for leaks.
10. Reconnect the battery, start the engine, and allow it to reach operating temperature while monitoring for proper function and any leaks.

Troubleshooting & FAQ

Q: How do I confirm this fits my engine?

A: This thermostat fits Mercury/Mariner 40, 50, and 60 HP 4-stroke EFI outboards with serial number 1C050252 and newer. The best way to ensure a match is to cross-reference your existing part number with one of the compatible numbers listed: 8M0117413, 8M0168892, or Sierra 18-3640.

Q: What are the symptoms of a bad thermostat?

A: Common signs of a failing thermostat include the engine overheating or, conversely, not reaching its proper operating temperature. You may also notice erratic readings on your temperature gauge or see coolant leaking from the thermostat housing area.

Q: At what temperature does this thermostat open?

A: This unit is rated to open at 122°F (50°C), ensuring your engine's cooling system activates at the correct temperature for efficient operation.

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.