Thermostat (140°F/60°C) – Fits Yamaha 20HP & 25HP Outboards (Replaces 6FM-12411-00-00)

Thermostat (140°F/60°C) – Fits Yamaha 20HP & 25HP Outboards (Replaces 6FM-12411-00-00)

This thermostat is designed for Yamaha 4-Stroke outboard engines, specifically compatible with 20HP (F20) models from 2018–2022 and 25HP (F25) models from 2016–2022.

It serves as a direct replacement for Yamaha part number 6FM-12411-00-00 and aftermarket part AM6FM-12411-00, ensuring reliable engine temperature regulation for optimal performance.

• Operating Temperature: 140°F (60°C)
• Installation: Direct OEM Replacement
• Construction: Built with corrosion-resistant metal for durability in both saltwater and freshwater environments.

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 Yamaha owners, here’s a guide to help you identify your engine’s serial/model: Yamaha Serial Number Guide. You can also review exploded diagrams to verify part numbers: Yamaha Parts Diagrams & Catalog.

Technical Specifications

Package Contents

• 1 x Thermostat (6FM-12411-00-00)

Installation Guide

1. Preparation: Ensure the engine is completely cool before starting. Disconnect the battery to prevent accidental starting.
2. Locate Thermostat Housing: Find the thermostat housing on the engine block, typically a small dome-shaped cover held on by two or three bolts.
3. Remove Housing Cover: Carefully loosen and remove the bolts securing the housing cover. Take note of the cover's orientation.
4. Extract Old Thermostat: Lift out the old thermostat and its gasket. Clean any old gasket material or corrosion from both the housing and cover surfaces.
5. Install New Thermostat: Insert the new thermostat, making sure it is correctly oriented (the spring side usually faces into the engine). Place the new gasket on top.
6. Reassemble: Reattach the housing cover in its original orientation and tighten the bolts evenly to the manufacturer's specified torque.
7. Final Checks: Reconnect the battery. Start the engine and immediately check for any water leaks around the thermostat housing. Allow the engine to warm up and monitor the temperature gauge to ensure it is stable.

Troubleshooting & FAQ

Q: How can I confirm this thermostat fits my Yamaha outboard?

A: This thermostat is designed for Yamaha 20HP (F20) models (2018–2022) and 25HP (F25) models (2016–2022). To be certain, verify your exact engine model and year against the "Compatible Engine Models" table and cross-reference the OEM part number 6FM-12411-00-00.

Q: What are the signs of a failing thermostat?

A: Common signs include the engine overheating at high speeds, running too cold at trolling speeds, or inconsistent temperature readings on your dashboard gauge. An engine alarm may also sound to indicate an overheating condition.

Q: How often should I replace my outboard's thermostat?

A: It is good practice to inspect the thermostat annually and consider replacing it every 2-3 years, or as part of your regular water pump service. Replacement is especially important if you operate frequently in saltwater environments, as salt can cause corrosion and sticking.

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.