Thermostat 50°C – Fits Yamaha 2-Stroke 3HP-250HP Outboards (Replaces 6E5-12411, 688-12411-10, 6H3-12411)

Thermostat 50°C – Fits Yamaha 2-Stroke 3HP-250HP Outboards

This thermostat is designed for a wide range of Yamaha 2-stroke outboard engines from 3 HP to 250 HP, covering models from 1984 to 2004. It also fits compatible Parsun and Makara Marine 2-stroke models.

Engineered to meet original equipment manufacturer (OEM) specifications, this part ensures a direct fit and reliable performance. It replaces multiple Yamaha part numbers, including 6E5-12411, 688-12411-10, and 6H3-12411.

• Operating Temperature: 50°C (122°F)
• Installation: Direct replacement with OEM fit
• Fuel Compatibility: Gasoline

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.

Confirm your engine model/year in the table below.

Yamaha 2-Stroke Outboard Engines

Parsun & Makara 2-Stroke Outboard Engines

Technical Specifications

Package Contents

1 x Thermostat (Replaces 6E5-12411-30-00, 6E5-12411-02, 688-12411-10-00)

Installation Guide

1. Ensure the engine is completely cool and disconnect the negative battery terminal for safety.
2. Locate the thermostat housing on the engine, typically on the cylinder head or block.
3. Place a drain pan under the engine and carefully drain the coolant to a level below the thermostat.
4. Remove the bolts securing the thermostat housing cover. Note their positions if they are different lengths.
5. Gently tap the housing cover to break the seal, then lift it off. Note the orientation of the old thermostat.
6. Remove the old thermostat and the gasket from the housing.
7. Thoroughly clean the mating surfaces of the housing and its cover to remove any old gasket material or corrosion.
8. Install the new thermostat, ensuring its orientation matches the one you removed.
9. Position the new gasket correctly on the housing.
10. Reinstall the housing cover and tighten the bolts evenly in a crisscross pattern to the manufacturer-specified torque.
11. Refill the cooling system with the appropriate coolant mixture.
12. Reconnect the battery, start the engine, and carefully check for any leaks around the thermostat housing as the engine warms up.

Troubleshooting & FAQ

Q: How do I confirm this thermostat fits my specific Yamaha engine?
A: First, check the "Compatible Engine Models" table on this page. Match your engine's model, horsepower (HP), and year range with the listed OEM part numbers. For further verification, you can use the Yamaha Serial Number Guide to identify your exact model.

Q: What are the common signs of a failing thermostat?
A: Key symptoms include the engine overheating at low speeds, running too cold at normal operating speeds, or taking much longer than usual to reach its proper operating temperature. These can indicate the thermostat is stuck closed or open.

Q: Is this the correct temperature rating for my engine?
A: This is a 50°C (122°F) thermostat. It is crucial to replace your existing thermostat with one that has the same temperature rating specified by your engine's manufacturer to ensure proper performance and prevent engine damage.

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.