Thermostat – Fits Yamaha 300-350HP 4-Stroke Outboard (Replaces 6AW-12411-00-00)

Product Details

This replacement Thermostat fits Yamaha 300-350HP 4-Stroke Outboard engines, specifically V8 models manufactured from 2007 through 2017. It is a critical component designed to regulate your engine's cooling system for optimal performance and longevity.

It serves as a direct interchange for OEM part number 6AW-12411-00-00 and aftermarket references including Sierra 18-3634 and EMP 6AW-12411-00-00.

• Engineered for direct OEM replacement fit and function.
• Essential for regulating the engine's operating temperature.
• Backed by a 12-month manufacturer warranty for peace of mind.

Part Number Matrix

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

Engine & Model Compatibility

Confirm your engine model and year in the table below to ensure accurate fitment.

Technical Specs

Product Type

Thermostat

Installation

Direct OEM replacement

Fuel Type

Gasoline

Housing Material

Metal

Housing Color

Silver/Metallic

Dimensions

Height: 6.0 in; Width: 6.0 in; Length: 6.0 in;

Function

For cooling system regulation

Warranty

12-month warranty (WATERLONG)

What’s in the Box

• 1 x Thermostat (6AW-12411-00-00)

Installation Notes

1. Ensure the engine is completely cool before beginning work. Disconnect the battery for safety.
2. Locate the thermostat housing on the engine block. Place a drain pan underneath to catch any residual coolant.
3. Carefully remove the bolts securing the housing cover. Note their placement and length if they differ.
4. Gently pry the housing cover off. If it's stuck, tap it lightly with a rubber mallet. Do not use a screwdriver, as this can damage the sealing surfaces.
5. Remove the old thermostat and any gasket or o-ring remnants. Clean both the housing and cover surfaces thoroughly.
6. Install the new thermostat, ensuring it is oriented correctly. Place the new gasket or o-ring into position.
7. Re-secure the housing cover, tightening the bolts in a crisscross pattern to the manufacturer's specified torque.
8. Refill the cooling system, reconnect the battery, and run the engine while checking for leaks and proper temperature gauge operation.

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.