Thermostat – Fits Yamaha 4-Stroke 80-100HP (Replaces 6D9-12411-00)

Thermostat – Fits Yamaha 4-Stroke 80-100HP (Replaces 6D9-12411-00)

This thermostat is engineered to fit a range of Yamaha 4-stroke outboard motors, specifically 80-100HP models including the F100D, F100A, F100B, and F80A series manufactured between 2005 and 2017.

It serves as a direct replacement for several OEM and aftermarket part numbers, ensuring compatibility and restoring proper engine temperature regulation for optimal performance and longevity.

• Operating Temperature: Maintains engine temperature at a consistent 55°C (131°F).
• Installation Method: Designed as a direct-fit replacement for the original part.
• Primary Component: The package includes one high-quality thermostat.

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 (6D9-12411-00)

Installation Guide

1. Safety First: Ensure the engine is cool and disconnect the battery terminals.
2. Drain Coolant: Place a container below and carefully drain the engine's cooling system.
3. Locate Housing: Find the thermostat housing on the engine block or cylinder head.
4. Remove Cover: Loosen and remove the bolts securing the thermostat housing cover.
5. Extract Old Part: Remove the old thermostat and its gasket. Note the orientation for correct placement of the new part.
6. Clean Surfaces: Thoroughly clean the gasket mating surfaces on both the housing and the cover.
7. Install New Thermostat: Insert the new thermostat, ensuring it is correctly seated, followed by the new gasket.
8. Secure Housing: Re-attach the housing cover and tighten the bolts to the manufacturer's specified torque.
9. Refill System: Refill the cooling system with the appropriate coolant.
10. Final Checks: Reconnect the battery, start the engine, and carefully check for any leaks around the housing.

Troubleshooting & FAQ

Q: How do I confirm this thermostat fits my engine?

A: The most reliable method is to check the part number 6D9-12411-00 against your engine's service manual or an official parts diagram. You should also verify your model and year in our "Compatible Engine Models" list above. For assistance, our Yamaha serial number guide can help you identify your engine details.

Q: What are the common symptoms of a failed thermostat?

A: A faulty thermostat can cause the engine to overheat (if stuck closed) or run too cool (if stuck open), leading to poor performance, increased fuel consumption, and potential engine damage. You may also notice erratic readings on your temperature gauge.

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

A: While there is no fixed interval, it is good practice to inspect the thermostat during routine cooling system service (e.g., every 2-3 years or 200-300 hours). Replacement is recommended if you notice signs of corrosion, sticking, or if the engine is not maintaining its correct operating temperature.

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.