Thermostat Repair Service Kit – Fits Mercury/MerCruiser 4.3L 5.0L 5.7L 7.4L V6 V8 SternDrive Motors (Replaces 807252Q4, 807252T4, 807252T7, 8M0089715)

Thermostat Repair Service Kit – Fits Mercury/MerCruiser 4.3L, 5.0L, 5.7L, 7.4L V6 & V8

This thermostat repair service kit is designed for a wide range of Mercury/MerCruiser V6 and V8 gasoline sterndrive engines (262-454 CID) manufactured between 1983 and 2016 with standard cooling systems. It maintains the correct engine operating temperature of 140°F (60°C) to ensure optimal performance, fuel efficiency, and engine longevity.

This kit is a direct replacement for Mercury/MerCruiser part numbers 807252Q4, 807252T4, 807252T7, and 8M0089715.

• Operating Temperature: Opens at a nominal 140°F (60°C).
• Engine Compatibility: Fits various GM-based V6 and V8 engines from 1983–2016.
• Complete Solution: Includes the thermostat and all necessary gaskets and seals for a full replacement.

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

This comprehensive kit includes the following components:

• 1 x Thermostat (8M6002714 / 59137)
• 1 x O-Ring (25-30224)
• 1 x Gasket, Thermostat Housing Cover (27-33179-2)
• 1 x Gasket, Thermostat Cover (27-41812)
• 1 x Gasket, Thermostat Housing (27-47510)
• 1 x Gasket, Lower Housing (27-530451 / 27-48818-1)
• 1 x Gasket (27-33918)

Installation Guide

Follow these general steps for installation. Always consult your engine’s service manual for detailed instructions and torque specifications.

1. Safety First: Ensure the engine is completely cool before starting.
2. Drain Coolant: Drain the engine coolant to a level below the thermostat housing.
3. Access Housing: Locate and remove the bolts securing the thermostat housing cover.
4. Remove Old Parts: Take out the old thermostat and gaskets. Note the orientation of the thermostat.
5. Clean Surfaces: Thoroughly clean the mating surfaces of the housing and cover, removing any old gasket material or sealant.
6. Install New Parts: Place the new thermostat and gaskets into the housing in the correct orientation.
7. Reassemble: Reattach the housing cover and tighten the bolts to the manufacturer's specified torque.
8. Refill System: Refill the cooling system with the appropriate coolant.
9. Final Check: Start the engine, check for any leaks, and monitor the temperature gauge to ensure it reaches and maintains the correct operating temperature.

Troubleshooting & FAQ

Q: How do I confirm this thermostat kit will fit my specific engine?
A: The best way to ensure fitment is to check the part number on your original thermostat. You can also use our Compatible Engine Models table to find your model, year, and serial number range. If you are still unsure, please contact our support team with your engine details.

Q: What are the signs of a failing thermostat?
A: Common symptoms include engine overheating, the engine not reaching normal operating temperature (running too cool), erratic temperature gauge readings, and potential coolant leaks around the thermostat housing.

Q: How often should I replace my engine's thermostat?
A: Thermostats are a critical maintenance item. It is recommended to replace them as part of a major cooling system service every 3-5 years, or immediately if you notice any signs of failure. Proactive replacement can prevent engine damage from overheating.

Q: Why is the 140°F temperature important for my marine engine?
A: This 140°F thermostat is specified for raw-water cooled engines to prevent salt and mineral buildup that can occur at higher temperatures, which could restrict cooling passages and lead to overheating.

Q: Is this an OEM part or an aftermarket replacement?
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.