140°F Thermostat & Gasket Kit – Fits Mercury Marine 8-35HP Outboards (Replaces 8M0119207, 855676002, 855676005)

140°F Thermostat & Gasket Kit – Fits Mercury Marine 8-35HP Outboards

This thermostat and gasket kit is designed for Mercury Marine 4-Stroke outboards from 8 to 35HP (2002–Present), including Carbureted, EFI, Jet, and SeaPro models. It ensures your engine maintains the correct operating temperature for optimal performance and longevity.

This assembly provides a direct replacement for Mercury part numbers 8M0119207, 855676002, and 855676005, along with several other aftermarket equivalents, ensuring a precise fit and reliable function.

• Engineered for a consistent 140°F (60°C) operating temperature.
• Features a self-cleaning design that allows cooling system contaminants to flush through closing surfaces.
• Kit includes one thermostat, one rubber seal, and one housing gasket for a complete installation.

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 855676002/8M0119207)
• 1 x Thermostat Rubber Seal
• 1 x Thermostat Housing Gasket (Replaces 27-853702005/27-898101194)

Installation Guide

1. Safety First: Ensure the engine is completely cool before beginning. Disconnect the battery to prevent any accidental starts.
2. Locate Housing: Find the thermostat housing on the engine block. It is typically a small dome-shaped cover where the main coolant hoses connect.
3. Drain Coolant: Place a drain pan under the engine and partially drain the cooling system to a level below the thermostat housing.
4. Remove Housing Cover: Loosen and remove the bolts securing the thermostat housing cover. A gentle tap may be needed to break the seal.
5. Remove Old Parts: Carefully lift out the old thermostat and its gasket or rubber seal. Note the orientation of the thermostat.
6. Clean Surfaces: Thoroughly clean the mounting surfaces of the housing and its cover, removing all old gasket material and corrosion.
7. Install New Thermostat: Place the new thermostat into the housing, ensuring it is oriented correctly (the "jiggle pin" or bleed hole should usually be at the top).
8. Install New Gasket: Position the new gasket and rubber seal as required by your model.
9. Re-secure Cover: Reinstall the housing cover and tighten the bolts evenly in a crisscross pattern to the manufacturer's specified torque. Do not overtighten.
10. Refill & Bleed System: Refill the cooling system with the appropriate coolant. Start the engine with the radiator cap off to allow air to bleed from the system. Top off as needed.
11. Check for Leaks: Once the engine reaches operating temperature, inspect the thermostat housing for any signs of leaks.

Troubleshooting & FAQ

Q: How can I confirm this thermostat fits my specific engine model?
A: The best way is to match your engine's serial number and model year against our compatibility chart. You can also compare the part number stamped on your old thermostat with the numbers listed in our Part Number Cross-Reference table. Using our linked Mercury resources can further help verify fitment.

Q: My engine is overheating. Could a faulty thermostat be the cause?
A: Yes, a stuck-closed thermostat is a common cause of overheating. Other signs of failure include erratic temperature gauge readings or the engine running too cool (stuck-open). This kit is designed to resolve such issues by restoring proper temperature regulation.

Q: What is the benefit of the 'self-cleaning' design?
A: The self-cleaning feature incorporates a design that helps flush small debris or contaminants out of the thermostat's closing mechanism. This reduces the risk of the thermostat sticking open or closed, leading to more reliable and consistent engine temperature control, especially in raw water cooling systems.

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.