Thermostat – Fits Yamaha 2-Stroke 3-250HP (Replaces 6E5-12411-30-00, 6E5-12411-20-00)

Product Details

This aftermarket Yamaha Outboard Thermostat is a crucial component for maintaining optimal engine temperature in a wide array of Yamaha 2-Stroke outboards. It is engineered to fit models from 9.9HP up to 250HP, covering engine years from 1994 to 2011 as detailed in our compatibility list.

It functions as a direct interchange for numerous OEM part numbers, including the primary replacement 6E5-12411-30-00, as well as superseded parts like 6E5-12411-20-00, 688-12411-10-00, and others, ensuring a precise fit for service and maintenance.

• Designed for direct, hassle-free installation as an OEM-equivalent part.
• Features a robust brass housing for superior corrosion resistance in marine environments.
• Maintains correct engine operating temperature to prevent overheating, reduce wear, and optimize fuel efficiency.

Part Number Matrix

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

Engine & Model Compatibility

Confirm your engine model and year in the table below. This part is designed for the specific Yamaha 2-Stroke outboard models listed.

Technical Specs

Product Type

Outboard Engine Thermostat

Installation

Direct OEM Replacement

Fuel Type

Gasoline

Housing Material

Brass

What’s in the Box

• 1 x Thermostat (6E5-12411-30-00)

Installation Notes

1. Disconnect the battery and ensure the engine is cool to the touch before starting.
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 if they are different lengths.
4. Remove the old thermostat and gasket. Clean both the housing and cover surfaces thoroughly, removing any old gasket material or corrosion.
5. Install the new thermostat in the correct orientation. A small marking or "jiggle pin" should typically face upwards.
6. Place the new gasket (sold separately) onto the housing, ensuring it is properly aligned with the bolt holes.
7. Re-install the housing cover and tighten the bolts to the manufacturer's specified torque in a crisscross pattern. Do not overtighten.
8. Reconnect the engine's cooling hoses and refill the cooling system with the appropriate fluid.
9. Reconnect the battery, start the engine, and let it run at idle. Check carefully for any coolant leaks around the housing.

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.