Thermostat with Gasket – Fits Yamaha Outboard 25-250 HP (Replaces 6E5-12411-10, 688-12411-10)

Thermostat with Gasket – Fits Yamaha Outboard 25-250 HP (Replaces 6E5-12411-10, 688-12411-10)

This thermostat assembly is designed for a wide range of Yamaha 2-stroke and 4-stroke outboard engines. It ensures your engine maintains the correct operating temperature for optimal performance and longevity. It is compatible with various Yamaha models from 9.9 HP to 250 HP, covering years from 1984 through 2008 and beyond for specific models.

This component is a direct replacement for multiple Yamaha part numbers, including the 6E5 and 688 series. Please refer to the cross-reference table and engine compatibility list below to ensure a correct fit for your specific model.

• Engineered to OEM specifications with an opening temperature of 50°C (122°F).
• Manufactured from high-quality stainless steel and brass for durability and corrosion resistance.
• Complete kit includes the thermostat, a matching gasket, and two seals for a comprehensive installation.

Part Number Cross-Reference

This part directly replaces multiple Yamaha OEM part numbers. The most current part number is 6E5-12411-30-00. Refer to the table below for the supersession history.

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 Outboard Engines

Yamaha 4-Stroke Outboard Engines

Technical Specifications

Package Contents

• 1 x Thermostat (6E5-12411-30-00)
• 1 x Thermostat Housing Gasket (61A-12414-A0-00)
• 2 x Thermostat Seals (688-12412-00)

Installation Guide

1. Disconnect the Battery: Always start by disconnecting the negative battery cable to prevent electrical shorts.
2. Drain Coolant: Partially drain the engine's cooling system to a level below the thermostat housing.
3. Locate and Remove Housing: Find the thermostat housing on the engine. Remove the bolts securing the cover.
4. Remove Old Thermostat: Carefully lift out the old thermostat. Pay close attention to its orientation.
5. Clean Surfaces: Thoroughly clean any old gasket material or sealant from both the housing and the engine mating surface.
6. Install New Components: Place the new thermostat into the housing in the correct orientation. Install the new gasket and seals as required.
7. Reassemble: Re-secure the thermostat housing cover, tightening the bolts to the manufacturer's recommended torque specification.
8. Refill and Check: Refill the cooling system. Reconnect the battery, start the engine, and let it warm up. Check for any leaks around the housing.

Troubleshooting & FAQ

How do I confirm this thermostat fits my specific Yamaha outboard?

The most reliable method is to cross-reference the OEM part number (6E5-12411-30-00) with your existing part. Additionally, please check the "Compatible Engine Models" tables on this page to verify your engine model, horsepower, and year range match the listing.

What are the common signs of a failing engine thermostat?

Signs of a faulty thermostat include the engine overheating (especially at idle or low speeds), taking too long to reach its proper operating temperature, or erratic temperature gauge readings. An engine alarm may also be triggered by an overheating condition.

At what temperature is this thermostat set to open?

This thermostat is calibrated to begin opening at 50°C (122°F), ensuring the engine warms up quickly and maintains a stable temperature for efficient operation.

Does this kit include everything I need for the replacement?

Yes, this is a complete kit that includes one thermostat, one thermostat housing gasket, and two thermostat seals. This provides the core components needed for a standard replacement job.

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.