6AH-12411-00 Thermostat for Yamaha F2.5MSH F9.9H F15C F20B | JLM Marine

6AH-12411-00 Thermostat for Yamaha F2.5MSH F9.9H F15C F20B

This 50℃ (122°F) thermostat is engineered to fit Yamaha 4-stroke outboard engines ranging from 2.5 HP to 70 HP. It provides precise temperature regulation for models including the F2.5MSH, F9.9H, F15C, and F20B series, as well as most Yamaha 4-stroke outboards from 1987 and up.

This aftermarket thermostat directly replaces Yamaha OEM part numbers 6AH-12411-00, 69M-12411-01, 69M-12411-00, 6G8-12411-00, and Sierra Marine 18-3624, ensuring broad compatibility across multiple engine families.

• Replaces multiple OEM and aftermarket part numbers for wide application
• Operating temperature: 50℃ / 122°F
• Direct fit for Yamaha 4-stroke outboards 9.9–70 HP (1987+)

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

Your order includes:

• 1 × 50℃ (122°F) Outboard Thermostat

Installation Guide

1. Ensure the engine is completely cool and disconnect the battery to prevent accidental starts.
2. Drain the cooling system following your engine's service manual procedures.
3. Locate the thermostat housing, typically positioned on the engine block or cylinder head. Remove the mounting bolts or clamps securing the housing cover.
4. Carefully lift off the housing cover and extract the old thermostat, noting its orientation.
5. Clean the mating surfaces of the housing and cover thoroughly, removing all old gasket material and debris.
6. Install the new thermostat in the same orientation as the original, ensuring the temperature sensor faces the correct direction.
7. Place a new gasket (if applicable) on the housing surface and carefully reposition the cover.
8. Torque the mounting bolts to the manufacturer's specifications in a cross-pattern to ensure even seating.
9. Refill the cooling system with the manufacturer-recommended coolant mixture.
10. Reconnect the battery and start the engine, allowing it to reach operating temperature.
11. Check for leaks around the thermostat housing and verify proper cooling system operation.
12. Top off coolant if necessary and dispose of old coolant responsibly.

Troubleshooting & FAQ

Q: How do I confirm this thermostat fits my Yamaha engine?
A: Cross-reference your engine model and year with the Compatible Engine Models table above. Verify your original thermostat's part number matches one of the OEM numbers listed (6AH-12411-00, 69M-12411-01, 69M-12411-00, or 6G8-12411-00). If your model year is 1987 or newer and falls within the 9.9–70 HP 4-stroke range, this thermostat should be compatible.

Q: How often should I replace my outboard thermostat?
A: Replace the thermostat every 2–3 years or per your engine manufacturer's maintenance schedule. If you notice overheating, poor temperature regulation, or corrosion on the existing thermostat, replace it immediately regardless of age.

Q: What are the signs that my thermostat is failing?
A: Common symptoms include engine overheating, unusually low operating temperature, fluctuating temperature gauge readings, or steam from the engine compartment. A stuck-closed thermostat causes overheating, while a stuck-open thermostat prevents the engine from reaching proper operating temperature.

Q: Can I install this thermostat myself, or do I need a mechanic?
A: If you have basic mechanical skills and follow the installation guide, you can replace the thermostat yourself. However, professional installation is recommended to ensure proper torque specifications, correct orientation, and complete system flushing.

Q: Is this an OEM part or an aftermarket replacement?
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.