Thermostat – Fits Yamaha 2-Stroke Outboards 3-250 HP (Replaces 6E5-12411-02-00, 6E5-12411-00-00)

Thermostat – Fits Yamaha 2-Stroke Outboards 3-250 HP

This thermostat is designed for a wide range of Yamaha 2-Stroke outboard motors, from 3 HP to 250 HP, covering models manufactured between 1984 and 2009. It ensures your engine maintains the correct operating temperature for optimal performance and longevity.

It serves as a direct replacement for multiple Yamaha, Sierra, and Parsun part numbers, providing broad compatibility across various engine models, including standard 2-stroke and HPDI systems.

• Installation Type: Direct replacement
• Operating Temperature: 50°C (122°F) opening temperature
• Package Includes: Thermostat and thermostat seal

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.

Yamaha 2-Stroke Outboards

Yamaha 2-Stroke HPDI Outboards

Parsun Outboards

Technical Specifications

Package Contents

• 1 x Thermostat (6E5-12411-02-00)
• 1 x Thermostat Seal

Explosion Diagram

Installation Guide

1. Safety First: Ensure the engine is off and cool. Disconnect the negative battery cable.
2. Drain Coolant: Place a drain pan under the engine and carefully drain the cooling system.
3. Locate Housing: Find the thermostat housing on the engine block. It is typically a small dome-shaped cover held by two or three bolts.
4. Remove Housing: Loosen and remove the bolts securing the housing cover. Gently tap the cover if it is stuck, but do not pry it.
5. Remove Old Parts: Take out the old thermostat and the rubber seal or gasket. Note the orientation of the thermostat.
6. Clean Surfaces: Thoroughly clean the mating surfaces of the housing and the engine block, removing any old gasket material or corrosion.
7. Install New Parts: Place the new thermostat into the housing in the correct orientation. Install the new thermostat seal.
8. Reassemble: Re-install the housing cover and tighten the bolts to the manufacturer's specified torque.
9. Refill Coolant: Refill the cooling system with the appropriate coolant mixture.
10. Check for Leaks: Reconnect the battery cable. Start the engine and let it run for several minutes, checking carefully for any coolant leaks around the housing.

Troubleshooting & FAQ

How do I confirm this thermostat fits my engine?
First, check the compatible engine model tables on this page. Cross-reference your engine's model, horsepower, and year. Second, use the Part Number Cross-Reference table to see if your old part number is listed. For Yamaha owners, our Yamaha Serial Number Guide can help you identify your model details.

What are the common signs of a failing thermostat?
Symptoms include engine overheating, the engine not reaching its normal operating temperature, erratic temperature gauge readings, or increased fuel consumption. A thermostat stuck open will prevent the engine from warming up, while one stuck closed will cause overheating.

Is a new seal included with this thermostat?
Yes, this kit includes both the thermostat and the required thermostat seal for a complete installation. Using a new seal is critical for preventing leaks.

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.