Thermostat Repair Service Kit for Mercruiser 4.3L 5.0L 5.7L 7.4L V6 V8 SternDrive Motors 807252Q4

Thermostat Kit 140°F – Fits MerCruiser 4.3L/5.0L/5.7L/7.4L V6/V8 SternDrive (Replaces 807252Q4)

This thermostat kit is designed for a wide range of Mercury MerCruiser V6 and V8 gasoline stern drive engines (262-454 CID) manufactured between 1983 and 2016 with standard cooling systems. It ensures your engine operates at the correct temperature for optimal performance and longevity.

It serves as a direct replacement for multiple OEM and aftermarket part numbers, providing a comprehensive solution for engine maintenance and repair. This kit is not intended for use in high-performance engine models.

• Operating Temperature: Maintains a consistent 140°F (60°C) engine temperature.
• Complete Solution: Includes the thermostat and all required gaskets and O-rings for a full replacement.
• Broad Compatibility: Fits a wide variety of MerCruiser models from 1983 to 2016.

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 (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

1. Safety First: Disconnect the boat's battery before beginning work.
2. Drain Coolant: Drain the engine coolant from the block to a level below the thermostat housing.
3. Locate Housing: Find the thermostat housing, typically located where the large coolant hose from the circulating pump connects to the top of the engine.
4. Remove Cover: Loosen and remove the bolts securing the thermostat housing cover.
5. Remove Old Parts: Carefully lift off the cover and remove the old thermostat and gasket. Note the orientation of the thermostat.
6. Clean Surfaces: Thoroughly clean the mating surfaces of the housing and cover, removing all old gasket material.
7. Install New Thermostat: Place the new 140°F thermostat into the housing, ensuring it is oriented correctly.
8. Install New Gaskets: Position the new gaskets as required by your specific engine model.
9. Reassemble: Reinstall the housing cover and tighten the bolts to the manufacturer's specified torque.
10. Refill Coolant: Refill the cooling system with the appropriate coolant mixture.
11. Check for Leaks: Reconnect the battery, start the engine, and let it warm up. Carefully check for any leaks around the thermostat housing.
12. Final Check: Once the engine reaches operating temperature, verify that the temperature gauge reads correctly and there are no leaks.

Troubleshooting & FAQ

How do I confirm this thermostat fits my MerCruiser engine?
This kit is designed for MerCruiser V6 and V8 engines (4.3L to 7.4L, or 262-454 CID) from 1983–2016 using a standard cooling system. To ensure a perfect match, please check your engine model and serial number against the "Compatible Engine Models" table. This kit does not fit high-performance models.

What is the operating temperature of this thermostat?
This is a 140°F (60°C) thermostat. This temperature rating is critical for raw water cooled marine engines to prevent salt and mineral buildup while ensuring the engine warms up to an efficient operating temperature.

My original part number is 807252T7. Will this kit work?
Yes. This kit is a direct aftermarket replacement for Mercury/MerCruiser part numbers 807252Q4, 807252T4, 807252T7, and 8M0089715, in addition to several other aftermarket brand numbers listed in the cross-reference table.

OEM vs. Aftermarket?
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.

How fast do you ship and how much does it cost?
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.

What is your warranty and return policy?
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.