Thermostat (130°F/54°C) – Fits Mercury/Mariner 200-250 HP 3.0L EFI/DFI (Replaces 885599004, 8M0057307)

Thermostat (130°F/54°C) – Fits Mercury/Mariner 200-250 HP 3.0L EFI/DFI

This aftermarket thermostat is designed for a wide range of Mercury and Mariner 200-250 HP, 3.0L V6 engines manufactured between 1997 and 2008, including both 2-Stroke DFI and 4-Stroke EFI models. It ensures your engine maintains the correct operating temperature for optimal performance and fuel efficiency.

It serves as a direct replacement for multiple OEM and aftermarket part numbers, offering a reliable and cost-effective solution for engine maintenance and repair.

• Operating Temperature: 130°F (54°C)
• Installation: Direct replacement for a straightforward fit.
• Compatibility: Replaces Mercury parts 885599003, 885599004, and 8M0057307.

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 Thermostat (Replaces 885599004/8M0057307)

Installation Guide

1. Safety First: Ensure the engine is cool and disconnect the battery cables.
2. Drain Coolant: Drain the engine's cooling system to a level below the thermostat housing.
3. Locate Housing: Find the thermostat housing on the engine block or cylinder head.
4. Remove Cover: Loosen and remove the bolts securing the housing cover.
5. Remove Old Thermostat: Note the orientation of the old thermostat before carefully removing it from the housing.
6. Clean Surfaces: Thoroughly clean the mating surfaces of the housing and cover, removing any old gasket material or sealant.
7. Install New Thermostat: Place the new thermostat into the housing, ensuring it is in the correct orientation.
8. Replace Cover: Position the new gasket (if applicable) and reinstall the housing cover, tightening the bolts to the manufacturer's specified torque.
9. Refill Coolant: Refill the cooling system with the appropriate coolant mixture.
10. Check for Leaks: Reconnect the battery, start the engine, and let it run until it reaches operating temperature, carefully checking for any leaks around the housing.

Troubleshooting & FAQ

Q: How do I confirm this thermostat fits my engine?

A: First, check your engine's model, horsepower, and year against the compatible models list above. For Mercury/Mariner engines, we highly recommend using the serial number lookup guides linked on this page to confirm your exact model. Finally, verify that your current part's number matches one of the cross-referenced part numbers: 885599003, 885599004, 8M0057307, 18-3535, or 775-15.

Q: What are the signs of a failing thermostat?

A: Common symptoms of a bad thermostat include the engine overheating, the engine failing to reach normal operating temperature (running too cold), erratic temperature gauge readings, and poor engine performance or increased fuel consumption.

Q: What temperature is this thermostat rated for?

A: This thermostat is designed to begin opening at 130°F (54°C) to allow coolant to circulate through the engine.

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.