Thermostat Repair Service Kit for Mercury Marine 2 Stroke 6-25 HP Outboard Motors 14586A3 (with O-ring)

Thermostat Kit – Fits Mercury/Mariner 6-25 HP 2-Stroke Outboards (Replaces 14586A3) (with O-ring)

This thermostat kit is designed for Mercury Marine 2-Stroke outboards from 6 HP to 25 HP, manufactured between 1986 and 1998+. It includes a 120°F (50°C) thermostat and all necessary gaskets for a complete and reliable service, ensuring your engine maintains the correct operating temperature for optimal performance and longevity.

This assembly is a direct replacement for multiple OEM and aftermarket part numbers, offering a reliable alternative to original components. It is engineered to meet or exceed original equipment specifications for fit and function.

• Includes the thermostat, seal, and gaskets required for a full replacement.
• Maintains proper engine operating temperature at 120°F (50°C).
• Engineered as a direct replacement for Mercury part 14586A3 and others.

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/Ring Rubber (62386001/27-62386)
• 1 x Thermostat Cover Gasket (14318/27-14318-3)
• 1 x Thermostat Gasket (19205/27-19205-1)

Installation Guide

1. Ensure the engine is off, cool to the touch, and the battery is disconnected.
2. Locate the thermostat housing on the engine block. Place a drain pan underneath it if necessary.
3. Carefully unbolt and remove the thermostat housing cover.
4. Take note of the old thermostat's orientation before removing it.
5. Remove the old thermostat, gaskets, and seals. Thoroughly clean any residue from the mating surfaces of the housing and cover.
6. Install the new thermostat in the same orientation as the original.
7. Position the new gaskets and seals correctly on the housing.
8. Re-install the housing cover and tighten the bolts evenly to the manufacturer-specified torque. Do not overtighten.
9. If coolant was drained, refill the cooling system according to your engine's service manual.
10. Reconnect the battery, start the engine, and carefully inspect the housing for any leaks.
11. Allow the engine to idle and monitor the temperature gauge to ensure it warms up to and maintains the correct operating temperature (around 120°F/50°C).

Troubleshooting & FAQ

How do I confirm this thermostat kit fits my Mercury outboard?

This kit is for Mercury/Mariner 6-25 HP 2-Stroke outboards (1986-1998+). The best way to confirm fitment is to match your engine's serial number to the ranges listed in the "Compatible Engine Models" table. Cross-referencing the part number from your old thermostat with our "Part Number Cross-Reference" table is also a reliable method.

What are the signs of a failing thermostat?

Common signs include the engine overheating or, conversely, failing to reach its normal operating temperature. An engine running too hot is at risk of severe damage, while an engine running too cold suffers from poor fuel efficiency, carbon buildup, and increased wear.

How often should I replace my outboard's thermostat?

It's wise to inspect the thermostat during your routine yearly water pump service, especially if you operate in saltwater. We recommend replacing it every 1-2 years or if you notice any corrosion, sticking, or erratic temperature readings to prevent engine issues.

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.