Thermostat Kit – Fits Mercury/Mariner 70-125 HP 2-Stroke (Replaces 803061T1)

Thermostat Kit – Fits Mercury/Mariner 70-125 HP 2-Stroke (Replaces 803061T1)

This thermostat kit is designed for Mercury/Mariner 70-125 HP 2-stroke inline 3 & 4 cylinder outboards from 1987 and newer. It ensures your engine maintains the correct operating temperature for optimal performance and longevity.

This kit serves as a direct replacement for several OEM and aftermarket part numbers, offering a reliable and cost-effective solution for your cooling system maintenance.

• Includes all necessary gaskets and seals for a complete installation.
• Engineered to meet or exceed OEM specifications for fit and function.
• Rated to open at 122°F / 50°C to regulate engine temperature.

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 (14586)
• 1 x Thermostat Seal (62386001)
• 1 x Thermostat Cover Gasket (430068)
• 1 x Washer (47533)

Installation Guide

Refer to your engine’s service manual for detailed instructions. The general steps for replacement are as follows:

1. Safety First: Disconnect the battery cables and ensure the engine is cool to the touch.
2. Drain Coolant: Place a container under the engine and carefully drain the cooling system.
3. Access Housing: Locate and remove the bolts securing the thermostat housing cover.
4. Remove Old Parts: Take out the old thermostat, gasket, and seal. Note their orientation.
5. Clean Surfaces: Thoroughly clean the mating surfaces of the housing and cover, removing any old gasket material or corrosion.
6. Install New Thermostat: Place the new thermostat into the housing, ensuring it is correctly oriented. Install the new gasket and seal.
7. Reassemble: Re-install the housing cover and tighten the bolts to the manufacturer's specified torque.
8. Refill System: Refill the cooling system with the recommended coolant.
9. Check for Leaks: Reconnect the battery, start the engine, and let it reach operating temperature. Carefully check for any leaks around the housing.

Troubleshooting & FAQ

Q: How can I be sure this thermostat kit fits my specific Mercury outboard?
A: The best way is to match your engine's serial number to the ranges listed in the "Compatible Engine Models" table. You can find your serial number on the engine's transom bracket. Our Mercury Serial Number Guide can help you locate it.

Q: What are the signs of a faulty thermostat?
A: Common symptoms include the engine overheating at various speeds or, conversely, failing to reach its normal operating temperature. An inaccurate temperature gauge reading can also indicate a problem.

Q: What temperature does this thermostat operate at?
A: This thermostat is designed to open at 122°F (50°C). This allows the engine to warm up quickly and then regulates the temperature to prevent overheating.

Q: How often should I replace my outboard's thermostat?
A: It is recommended to replace the thermostat and gaskets as part of your regular cooling system service, typically every 1-2 years or 100-200 hours, especially if operating in saltwater. Always refer to your owner's manual for specific maintenance intervals.

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.