Thermostat Kit – Fits Yamaha 2-Stroke 75-250 HP (Replaces 6E5-12411-30-00, 688-12411, 688-12414)

Thermostat Kit – Fits Yamaha 2-Stroke 75-250 HP

This thermostat kit is designed to fit a wide range of Yamaha 2-stroke outboard motors from 75 HP to 250 HP, including popular models such as the Z150, Z175, Z200, 115TLR, 150TXR, and 200TXR (2003–2014). It also covers various lower horsepower models from 9.9 HP to 50 HP.

It serves as a direct replacement for multiple Yamaha and aftermarket part numbers, ensuring compatibility and restoring proper engine operating temperature. Built with corrosion-resistant materials, this kit is engineered for reliability in marine environments.

• Direct Replacement: Installs using original mounting hardware without modifications.
• Operating Temperature: Activates at 50°C (122°F) to regulate engine temperature.
• Complete Kit: Includes the thermostat, 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 688-12411)
• 1 x Thermostat Housing Gasket (Replaces 688-12414)
• 1 x Thermostat Seal

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 drain the cooling system.
3. Locate Housing: Find the thermostat housing on the engine block or cylinder head.
4. Remove Cover: Loosen and remove the bolts securing the thermostat housing cover.
5. Remove Old Parts: Carefully take out the old thermostat and gasket. Note their orientation.
6. Clean Surfaces: Thoroughly clean the mating surfaces of the housing and cover, removing all old gasket material.
7. Install New Gasket: Place the new gasket (and seal, if applicable) onto the housing, ensuring it aligns correctly.
8. Install New Thermostat: Insert the new thermostat in the correct orientation.
9. Reassemble: Re-install the housing cover and tighten the bolts to the manufacturer's specified torque.
10. Refill Coolant: Refill the cooling system with the appropriate coolant mixture.
11. Check for Leaks: Reconnect the battery, start the engine, and let it warm up. Check carefully for any leaks around the housing.

Troubleshooting & FAQ

Q: How do I confirm this thermostat kit fits my engine?
A: Check your engine's model and year against the compatibility tables above. We also recommend using the Yamaha Serial Number Guide linked above to verify your exact model before ordering.

Q: What are the common signs of a failing thermostat?
A: A thermostat stuck open can cause the engine to warm up very slowly or run too cool. A thermostat stuck closed will cause the engine to overheat, especially at idle or low speeds, and may trigger an alarm.

Q: At what temperature does this thermostat open?
A: This thermostat is rated to open at 50°C (122°F), which is the standard specification for the listed Yamaha models to ensure optimal engine performance.

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.