Yamaha Outboard Thermostat Kit – 50°C (122°F) – Replaces 6E5-12411-30 and 688-12411
Yamaha Outboard Thermostat Kit – 50°C (122°F) – Replaces 6E5-12411-30 and 688-12411 is backordered and will ship as soon as it is back in stock.
Worry-free returns
Worry-free returns
Shop with confidence. If you’re not completely satisfied, eligible items may be returned within the return window, provided they are unused and in original packaging.
If the return is due to our error or a defective item, we’ll make it right.
Please contact us before returning any item.
Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
International delivery times may vary due to customs processing.
Tracking information will be provided once your order ships.
Yamaha Outboard Thermostat Kit – 50°C (122°F) – Replaces 6E5-12411-...
Yamaha Outboard Thermostat Kit – 50°C (122°F) – Replaces 6E5-12411-30 and 688-12411 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket Yamaha outboard thermostat kit is designed to help regulate engine operating temperature in compatible Yamaha marine gasoline outboards. The thermostat is rated at 50°C (122°F) for applicable 2-stroke installations and is supplied with the associated installation gasket and seal.
This replacement is cross-referenced to Yamaha part numbers including 6E5-12411-30 and the 688-12411 series. Always compare the part number, engine model, year, serial-number range, and the original component before ordering.
- Aftermarket direct-replacement thermostat for compatible Yamaha outboards.
- Designed for marine gasoline engine applications.
- Kit includes one thermostat, one housing gasket, and one thermostat seal.
- 50°C (122°F) temperature rating for applicable 2-stroke applications.
Part Number Matrix
The following references are associated with this replacement. A reference number alone does not confirm fitment for every engine model.
| Brand | Part Number |
|---|---|
| Sierra | 18-3540 |
| Sierra | 18-3622 |
| GHmarine | 18-3540 |
| QuickMarine | 18-3622 |
| Yamaha | 688-12411-00 |
| Yamaha | 688-12411-01 |
| Yamaha | 688-12411-10 |
| Yamaha | 688-12411-11 |
| Yamaha | 6E5-12411-10 |
| Yamaha | 6E5-12411-20 |
| Yamaha | 6E5-12411-30 |
Engine & Model Compatibility
The references below represent reported compatibility applications for this thermostat family. Confirm the exact engine model, year, serial-number range, stroke, and original part number before purchase. Models within the same horsepower family may use different thermostat specifications.
| Brand | Model | Rated HP | Stroke | Associated OEM Part No. | Fitment Note |
|---|---|---|---|---|---|
| Yamaha | 75C | 75 | 2-Stroke | 688-12411; 6E5-12411-30 | Verify year and serial range. |
| Yamaha | 90A | 90 | 2-Stroke | 688-12411; 6E5-12411-30 | Verify year and serial range. |
| Yamaha | 100A | 100 | 2-Stroke | 688-12411; 6E5-12411-30 | Verify year and serial range. |
| Yamaha | 115C | 115 | 2-Stroke | 688-12411; 6E5-12411-30 | Verify year and serial range. |
| Yamaha | 130B | 130 | 2-Stroke | 688-12411; 6E5-12411-30 | Verify year and serial range. |
| Yamaha | 150F, Z150P, Z150Q | 150 | 2-Stroke | 688-12411; 6E5-12411-30 | Verify year and serial range. |
| Yamaha | 175D, Z175G | 175 | 2-Stroke | 688-12411; 6E5-12411-30 | Verify year and serial range. |
| Yamaha | 200F, 200G, Z200N, Z200P | 200 | 2-Stroke | 688-12411; 6E5-12411-30 | Verify year and serial range. |
| Yamaha | 225D | 225 | 2-Stroke | 688-12411; 6E5-12411-30 | Verify year and serial range. |
| Yamaha | 250B | 250 | 2-Stroke | 688-12411; 6E5-12411-30 | Verify year and serial range. |
| Yamaha | Various models | 3–70 | 2-Stroke | 6E5-12411; 688-12411 | Reported cross-reference; verify the specific engine. |
| Yamaha | F2.5M | 2.5 | 4-Stroke | Not specified | Confirm the original thermostat number and dimensions. |
| Yamaha | Various F-series models | 2.5–100 | 4-Stroke | Not specified | General application range; model-specific confirmation is required. |
Technical Specifications
- Product Type
- Marine outboard engine thermostat kit
- Replacement Type
- Aftermarket replacement
- Installation
- Direct replacement where the listed part number and engine application match
- Engine Fuel
- Gasoline marine outboard applications
- Housing Material
- Metal thermostat construction
- Operating Temperature
- 50°C (122°F) for applicable 2-stroke applications
What’s in the Box
- 1 × thermostat, cross-referenced to 688-12411 and 6E5-12411-30
- 1 × thermostat housing gasket, cross-referenced to 688-12414
- 1 × thermostat seal, cross-referenced to 688-12412
Installation Notes
- Allow the engine to cool completely before servicing and follow the manufacturer's safety procedures.
- Locate the thermostat housing and place the engine in a stable, accessible position.
- Remove the housing cover, keeping track of bolt positions and any retaining hardware.
- Remove the old thermostat, gasket, and seal. Clean the mating surfaces without damaging the housing.
- Install the replacement thermostat in the same orientation as the original component, then fit the new gasket and seal.
- Reinstall the housing cover and tighten the fasteners to the manufacturer's specified torque.
- Run the engine according to the manufacturer's procedure and check for leaks, proper water flow, and abnormal temperature warnings.
Troubleshooting & FAQ
How do I confirm fitment?
Match the old thermostat's manufacturer part number to the references listed above, then confirm the engine model, year, serial-number range, stroke, and thermostat specification. Horsepower alone is not sufficient to confirm fitment.
What is the operating temperature?
The listed rating is 50°C (122°F) for applicable 2-stroke applications. Do not assume that every 4-stroke application uses the same temperature rating; confirm the requirement for the specific engine.
What are common signs of a failing thermostat?
Possible symptoms include overheating, slow warm-up, an abnormal temperature warning, reduced performance, or steam and unusual exhaust behavior. Diagnose the cooling system before replacing parts.
Does the kit include the gasket and seal?
Yes. The package includes one thermostat, one thermostat housing gasket, and one thermostat seal.
What is the difference between the 6E5-12411 and 688-12411 references?
These references are associated with Yamaha thermostat applications and may represent different engine series or revisions. Confirm the complete part number and engine application rather than relying on the base number alone.
Is this an OEM part?
No. This listing is for an aftermarket replacement intended for compatible applications and is not manufactured by Yamaha.
What are the shipping and return terms?
Standard shipping and return terms are shown at checkout and in the store's current policies. Keep the item unused and in its original condition if a return is required.
Safety & Important Information
- Verify the complete part number, engine model, year, serial range, stroke, and original component before ordering.
- Do not install a thermostat with a different temperature rating or physical design unless the manufacturer's application data confirms it.
- This is an aftermarket replacement, not an OEM Yamaha component.
- Professional installation is recommended when the correct service procedure or torque specification is unavailable.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for dependable service in real-world operating conditions.
- Global Fulfillment — Shipping options and estimated delivery times are displayed for the destination at checkout.
- Manufacturer-Direct Value — Competitive pricing with attention to product consistency and application details.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
