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

Product Details

This replacement Thermostat – Fits Yamaha 2-Stroke Outboards 3-250 HP and is engineered to regulate engine temperature for optimal performance. It's designed for a wide range of Yamaha 2-stroke outboard engines from 3 HP to 250 HP, including standard and HPDI models manufactured between 1984 and 2009.

It serves as a direct replacement for multiple Yamaha, Sierra, and Parsun part numbers, ensuring broad compatibility and a reliable fit for your specific engine model.

• Installs as a direct-fit replacement for the original thermostat.
• Constructed from durable brass and stainless steel for corrosion resistance.
• Includes a new thermostat seal for a complete installation.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Engine & Model Compatibility

Confirm your engine model/year in the table below.

This thermostat fits a comprehensive range of Yamaha outboards, including standard 2-stroke, HPDI, and smaller portable models.

It is also a compatible service part for various Parsun 2-stroke outboards.

Technical Specs

Product Type

Thermostat

Installation

Direct replacement

Fuel Type

Gasoline

Connection

Direct mount to engine block

Housing Material

Brass/stainless steel

Temperature Rating

50°C (122°F) opening temperature

Cooling System

For closed cooling system

Product Dimensions

5.5" x 5.5" x 5.5"

Box Dimensions

5.5" x 5.5" x 5.5"

What’s in the Box

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

Installation Notes

1. Ensure the engine is completely cool and disconnect the battery for safety.
2. Locate the thermostat housing on the engine block. Place a drain pan underneath if needed to catch any residual coolant.
3. Carefully remove the bolts securing the thermostat housing cover.
4. Remove the old thermostat and the existing seal or gasket. Clean both mating surfaces thoroughly to remove any old gasket material or corrosion.
5. Install the new thermostat, ensuring it is oriented correctly. Place the new thermostat seal in position.
6. Re-secure the housing cover, tightening the bolts to the manufacturer's specified torque in a crisscross pattern.
7. Reconnect the battery, refill the cooling system as needed, and start the engine.
8. Check for any leaks around the thermostat housing as the engine warms up.

Troubleshooting & FAQ

Safety & Important Info

• Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
• This is an aftermarket replacement, not an OEM component.
• Professional installation is recommended for safety and performance.

About Sea Sierra

• Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
• Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
• Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.