Thermostat – Fits Cummins MerCruiser QSD 2.8L & 4.2L Diesel Engines (Replaces 8M0093561, 879194215)

Thermostat – Fits Cummins MerCruiser QSD 2.8L & 4.2L Diesel Engines (Replaces 8M0093561, 879194215)

This thermostat is engineered for Cummins MerCruiser Diesel (CMD) 2.8L and 4.2L QSD marine engines. It ensures your engine maintains the correct operating temperature for optimal performance and efficiency.

This serves as a direct replacement for Mercury MerCruiser part numbers: 8M0093561, 879194215, 879194233, and 39012036F.

• Fuel Type Compatibility: Diesel
• Operating Temperature: Opens at 80°C (176°F)
• Quality Standard: Manufactured to OEM specifications in an ISO9002 certified factory

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 (8M0093561)

Installation Guide

1. Ensure the engine is completely cool before beginning work.
2. Carefully drain the engine coolant to a level below the thermostat housing.
3. Locate and remove the bolts securing the thermostat housing cover.
4. Take out the old thermostat and gasket, noting its orientation for correct placement of the new one.
5. Thoroughly clean the mating surfaces of the thermostat housing and its cover.
6. Install the new thermostat in the correct orientation.
7. Position the new gasket and reinstall the housing cover, tightening the bolts to the manufacturer's recommended torque specifications.
8. Refill the cooling system with the appropriate type and amount of coolant.
9. Start the engine, check for leaks, and monitor the temperature gauge to ensure the thermostat opens correctly as the engine warms up.

Troubleshooting & FAQ

Q: How can I be sure this thermostat fits my specific Cummins MerCruiser engine?

A: This thermostat is designed for CMD QSD 2.8L and 4.2L models. Please cross-reference your existing part number with the numbers listed (8M0093561, 879194215, 879194233) and verify your model is in the compatibility table on this page.

Q: What are the signs of a faulty thermostat?

A: Common symptoms include engine overheating, temperature gauge readings that are unusually high or low, erratic temperature fluctuations, and coolant leaks around the thermostat housing.

Q: What is the opening temperature of this thermostat?

A: This thermostat begins to open at 80°C (176°F) to regulate the engine's operating temperature, conforming to factory specifications for optimal engine health.

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.