Thermostat – Fits Yamaha 9.9-70 HP 4-Stroke Outboards (Replaces 6G8-12411-00, 69M-12411-00)

Thermostat – Fits Yamaha 9.9-70 HP 4-Stroke Outboards

This aftermarket thermostat is designed for a precise fit on a wide range of Yamaha 4-Stroke outboard motors from 9.9 to 70 HP (1987–present), including F9.9, F15, F20, F25, F40, F50, F60, and F70 models. It ensures your engine maintains the correct operating temperature for optimal performance and fuel efficiency.

Engineered as a direct replacement for multiple Yamaha and Sierra part numbers, this component restores original functionality and prevents overheating issues. The kit includes all necessary seals for a complete and reliable installation.

• Regulates engine temperature at a fixed 50°C (122°F).
• Made from a corrosion-resistant alloy for marine environments.
• Includes a thermostat, gasket, and O-ring for a complete installation.

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 × 50°C / 122°F Outboard Thermostat
• 1 × Gasket
• 1 × O-ring

Installation Guide

1. Disconnect Power: Disconnect the battery and ensure the engine is cool.
2. Access Housing: Locate and remove the thermostat housing cover, which is typically attached with two or three bolts.
3. Remove Old Thermostat: Carefully lift out the old thermostat and its gasket or seals. Note the orientation of the old part.
4. Clean Surfaces: Thoroughly clean the thermostat housing and cover surfaces, removing any old gasket material or corrosion.
5. Install New Thermostat: Place the new gasket and thermostat into the housing. Important: Ensure the spring assembly of the thermostat faces downwards, towards the engine block.
6. Reassemble: Reinstall the housing cover and tighten the bolts to the manufacturer's specified torque.
7. Test: Reconnect the battery and run the engine, checking for leaks around the housing.

Troubleshooting & FAQ

Q: How do I confirm this thermostat fits my engine?
A: Start by checking the "Compatible Engine Models" and "Part Number Cross-Reference" tables on this page. For Yamaha engines, you can use the linked serial number guides and parts catalogs to verify the exact OEM part number required for your specific model and year.

Q: What are the signs of a failing thermostat?
A: Common symptoms include engine overheating (if the thermostat is stuck closed) or the engine not reaching its proper operating temperature (if stuck open), which can lead to poor performance, increased fuel consumption, and carbon buildup.

Q: How should this thermostat be installed?
A: The thermostat should be installed with the spring assembly facing downwards, towards the engine block. Always replace the gasket and any O-rings during installation to ensure a proper seal. Refer to the installation guide above for a step-by-step process.

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.