6E5-12411-02 Outboard Thermostat for Yamaha 2 Stroke | JLM Marine

6E5-12411-02 Outboard Thermostat for Yamaha 2-Stroke Engines

This aftermarket replacement thermostat is designed for a wide range of Yamaha 2-stroke outboard engines from 9.9 HP to 250 HP, spanning model years from the mid-1980s through 2006. It ensures proper temperature regulation across numerous series including standard, commercial (C), precision blend (P), saltwater (S), and high-performance (V, VZ, Z) models.

This thermostat directly replaces multiple Yamaha OEM part numbers (6E5-12411-00, 6E5-12411-01, 6E5-12411-02-00, 6E5-12411-10, 6E5-12411-20, 6E5-12411-30-00) and aftermarket equivalents such as Sierra 18-3540, providing broad cross-platform compatibility.

• Fits: Yamaha 2-stroke outboards from 9.9 HP to 250 HP
• Application: Cooling system temperature control
• Direct OEM & aftermarket replacement

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 × Outboard Thermostat (6E5-12411-02)

Installation Guide

1. Disconnect the battery and allow the engine to cool completely before beginning work.
2. Locate the thermostat housing on your Yamaha outboard—typically mounted on the cylinder head or mid-section.
3. Remove the bolts or screws securing the thermostat cover and carefully lift it off.
4. Note the orientation of the old thermostat (spring side typically faces inward toward the engine).
5. Remove the old thermostat and thoroughly clean all gasket surfaces on both the housing and cover.
6. Inspect the mating surfaces for corrosion, cracks, or warping; replace seals or gaskets as needed.
7. Install the new thermostat in the same orientation as the original, ensuring it seats fully.
8. Apply a thin bead of marine-grade gasket sealant if your model requires it (check your service manual).
9. Reattach the thermostat cover and torque fasteners to manufacturer specifications in a cross-pattern.
10. Reconnect the battery, start the engine, and monitor for proper operating temperature and coolant flow.
11. Check for leaks around the thermostat housing during the first few minutes of operation.
12. If overheating or cooling issues persist, verify water pump function and inspect the cooling passages for blockages.

Troubleshooting & FAQ

Q: How do I confirm this thermostat fits my Yamaha outboard?
A: Cross-reference your engine model, horsepower, and year with the compatibility table above. You can also check your engine's parts diagram using the Yamaha Parts Catalog link provided or match your existing thermostat's OEM part number against the cross-reference table.

Q: What are the signs that my thermostat needs replacement?
A: Common symptoms include engine overheating, failure to reach normal operating temperature, steam from the powerhead, reduced cooling water discharge, or a temperature warning alarm. A stuck-closed thermostat causes overheating; a stuck-open thermostat prevents the engine from warming up properly.

Q: How often should I replace the outboard thermostat?
A: Yamaha recommends inspecting the thermostat during routine service intervals (typically every 100 hours or annually). Replace it every 2–3 years or sooner if you notice cooling issues, corrosion, or if it fails to open/close at the correct temperature during testing.

Q: Can I test the thermostat before installing it?
A: Yes. Submerge the thermostat in a pot of water with a thermometer, heat gradually, and observe the opening temperature (typically around 140–160°F / 60–71°C for most Yamaha 2-strokes). The thermostat should open smoothly and close when cooled. Discard if it sticks or opens at the wrong temperature.

Q: Is this an OEM part or aftermarket replacement?
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.