Thermostat Service Kit – Fits Mercury/Mariner V6 & V8 175HP-300HP (Replaces 8M0162139, 8M0137816)

Thermostat Service Kit – Fits Mercury/Mariner V6 & V8 175HP-300HP (Replaces 8M0162139, 8M0137816)

This thermostat service kit is designed for Mercury/Mariner 175-300HP, 3.4L V6 & 4.6L V8, 4-Stroke outboard engines from 2013 and up, with serial number 2B529482 and higher. It ensures your engine maintains the correct operating temperature for optimal performance and longevity.

This kit is a direct replacement for several OEM and aftermarket part numbers, including Mercury 8M0137816, Mercury/Quicksilver 8M0162139, Recmar 8M0162139, and JLM Marine 8M0162139.

• Installation Type: Direct replacement
• Operating Temperature: 60°C (140°F)
• Primary Use: Regulates engine temperature in Mercury outboard cooling systems

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 Kit (8M0162139)

Installation Guide

Follow these steps for proper installation. Ensure the engine is cool and disconnected from the power source before starting.

1. Safety First: Turn the engine off and allow it to cool completely. Disconnect the battery cables.
2. Drain Coolant: Place a container under the engine and carefully drain the cooling system.
3. Locate Housing: Identify the thermostat housing on the engine block.
4. Remove Cover: Loosen and remove the bolts securing the thermostat housing cover. Note their positions.
5. Extract Old Thermostat: Carefully remove the old thermostat and the gasket or sealing ring.
6. Clean Surfaces: Thoroughly clean the mating surfaces of the housing and its cover, removing any old gasket material or corrosion.
7. Install New Kit: Place the new thermostat from the kit into the housing, ensuring it is oriented correctly. Install the new gasket.
8. Secure Cover: Re-attach the housing cover and tighten the bolts in a crisscross pattern to the manufacturer's specified torque.
9. Refill System: Refill the cooling system with the appropriate coolant.
10. Reconnect Battery: Reconnect the battery cables securely.
11. Check for Leaks: Start the engine and let it run, checking carefully for any leaks around the thermostat housing.
12. Verify Temperature: Monitor the engine temperature gauge to ensure it warms up to the correct operating temperature and remains stable.

Troubleshooting & FAQ

How do I confirm this thermostat kit fits my engine?
This kit is specifically designed for Mercury/Mariner V6 (3.4L) and V8 (4.6L) 4-stroke outboards from 2013 and newer, with serial numbers 2B529482 and higher. The best way to ensure compatibility is to cross-reference your engine's model, year, and serial number against the "Compatible Engine Models" list provided on this page.

What are the signs of a failing thermostat?
Common symptoms include the engine overheating at high speeds, running too cold at idle, or inconsistent temperature gauge readings. A thermostat stuck open will prevent the engine from reaching its optimal operating temperature of 60°C (140°F), while a thermostat stuck closed will cause rapid overheating.

How often should the thermostat be replaced?
While there's no fixed interval, it is recommended to inspect the thermostat during routine cooling system service (e.g., every 300 hours or 3 years). You should replace it if you notice any signs of corrosion, sticking, or if the engine temperature becomes irregular.

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.