Yamaha 25-90HP 2-Stroke Thermostat 50C 688-12411-10
6E5-12411-30
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Yamaha 2-Stroke 50°C Thermostat
Aftermarket replacement | 688-12411-10 / 6E5-12411-30
A 50°C / 122°F replacement thermostat for specific Yamaha two-stroke outboards. This cooling-system service part is catalogued against Yamaha 688-12411-10 and related 688/6E5 references and should be selected by exact model code and original part number.
Key Features
- 50°C thermostat: Listed opening temperature of 122°F / 50°C.
- Aftermarket replacement: Not supplied as a Yamaha Genuine Part.
- Exact model-code guidance: Covers named 25, 30, 75, 80, 85 and 90HP two-stroke families.
- Cooling-system service item: Replaces a thermostat that is sticking, corroded or outside specification.
- Reference-led selection: Primary Yamaha reference 688-12411-10; current 4Boats SKU 6E5-12411-30.
Technical Specs
| Part type | Outboard cooling-system thermostat |
| Engine cycle | Two-stroke applications listed below |
| Opening temperature | 50°C / 122°F |
| Supply type | Aftermarket replacement |
| Primary Yamaha reference | 688-12411-10 |
| 4Boats SKU | 6E5-12411-30 |
Compatibility / Fitment Guide
Catalogued Yamaha model codes:
| HP family | Model codes | Fitment rule |
|---|---|---|
| 25HP | 25JEO, 25J, 25ESH | Confirm 688-12411-10 or listed supersession. |
| 30HP | 30DETO, 30DMH, 30MLH, 30DEO, 30ELH | Check full suffix and serial-specific diagram. |
| 75HP | 75CETO, 75TLR, 75AE, E75B | Do not apply to every 75HP generation. |
| 80–85HP | 80AEO, 80AET, 80AEM; 85A, 85AE | Match model code and reference. |
| 90HP | 90AET, 90TLRC, 90AEO | Match model code and reference. |
Not universal: Excludes four-stroke engines and any two-stroke whose diagram specifies a different temperature, diameter or Yamaha part number.
Part Number Cross Reference
| Yamaha | 688-12411-10; 688-12411-11; 6E5-12411-30 |
| Sierra | 18-3540 |
| Mallory | 9-43035 |
| 4Boats SKU | 6E5-12411-30 |
Cross-reference numbers identify the intended application; this listing is an aftermarket replacement unless explicitly stated otherwise.
Frequently Asked Questions
Is this a genuine Yamaha thermostat?
No. It is an aftermarket replacement.
Will it fit every Yamaha 25–90HP two-stroke?
No. It fits only specified model/serial applications. Compare the full model code and original thermostat reference.
What is the temperature rating?
50°C / 122°F.
Is a gasket included?
The current listing identifies the thermostat; do not assume a gasket is included unless shown in the product images or stated on the packaging.
Service the cooling system with the engine cold. Follow the Yamaha workshop procedure and use the specified seal/gasket and tightening torque for the exact engine.
For the products under £150 the shipping is £6.99.
Free delivery for most items over £150.
