Thermostat – Fits Yamaha 2-Stroke Outboard 75-250 HP (Replaces 6E5-12411-30-00, 688-12411 Series)

Thermostat – Fits Yamaha 2-Stroke Outboard 75-250 HP (Replaces 6E5-12411-30-00, 688-12411 Series)

This thermostat is designed for a wide range of Yamaha 2-Stroke outboard engines from 75 to 250 HP, covering models from 1991 to 2005. It ensures your engine maintains the correct operating temperature for optimal performance and longevity.

It serves as a direct replacement for multiple Yamaha and aftermarket part numbers, including the 6E5-12411-30-00 and 688-12411 series.

• Operating Temperature: Opens at 50°C / 122°F.
• Installation Type: Direct replacement for a straightforward installation.
• Complete Kit: Includes the thermostat, housing gasket, and seal for a comprehensive service.

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.

Technical Specifications

Package Contents

• 1 x Thermostat (Replaces 6E5-12411-30-00 / 688-12411 series)
• 1 x Thermostat Housing Gasket (Replaces 688-12414-A1 / 688-12414-00 / 688-12414-A0)
• 1 x Thermostat Seal (Replaces 688-12412)

Installation Guide

1. Safety First: Disconnect the battery and ensure the engine is cool before starting.
2. Drain Coolant: Place a drain pan under the engine and carefully drain the cooling system.
3. Locate Housing: Find the thermostat housing, typically on top of the cylinder head or near the intake manifold.
4. Remove Housing Cover: Loosen and remove the bolts securing the housing cover. Note their positions for reassembly.
5. Remove Old Thermostat: Carefully lift out the old thermostat and its gasket or seal.
6. Clean Surfaces: Thoroughly clean the mating surfaces of the housing and cover, removing all old gasket material and corrosion.
7. Install New Thermostat: Place the new thermostat into the housing, ensuring it is oriented correctly. Install the new gasket and seal.
8. Reassemble: Reattach 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, start the engine, and allow it to reach operating temperature. Carefully check for any leaks around the thermostat housing.

Troubleshooting & FAQ

Q: How do I confirm this fits my engine?
A: Start by checking your engine's model, year, and horsepower against the compatibility table. The most reliable method is to cross-reference the OEM part number stamped on your old thermostat. This part replaces Yamaha OEM number 6E5-12411-30-00 and others in the 688-12411 series.

Q: What are the symptoms of a bad thermostat?
A: Common signs of failure include the engine overheating, the engine not reaching its normal operating temperature (running too cold), or erratic readings on the temperature gauge. A stuck-open thermostat can cause poor fuel economy, while a stuck-closed one will lead to overheating.

Q: At what temperature does this thermostat open?
A: This thermostat is designed to start opening at 50°C (122°F), ensuring your engine warms up quickly and then maintains a stable temperature.

Q: OEM vs. Aftermarket?
A: 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.

Q: How fast do you ship and how much does it cost?
A: 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.

Q: What is your warranty and return policy?
A: 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.