Thermostat Kit 6E5-12411-30 18-3540 with Gasket for Yamaha 9.9 15 HP 2 Stroke Outboard 1984-2017
Thermostat Kit 6E5-12411-30 18-3540 with Gasket for Yamaha 9.9 15 HP 2 Stroke Outboard 1984-2017
Product Overview
Thermostat kit for Yamaha 9.9 and 15 HP two stroke outboards built from 1984 to 2017. It replaces Yamaha 6E5-12411-30 and the earlier 6E5-12411-20-00, 6E5-12411-10-00, 688-12411-10-00, 688-12411-11-00, 688-12411-01, 688-12411-00-00 and 688-12411-01-00, crosses to Mallory 9-43035 and Sierra 18-3540, and the kit carries the thermostat, its seal and the housing gasket.
These small two strokes are often used on tenders and trolling boats where the motor idles for hours. That is the duty that sludges a thermostat closed, and the symptom is a motor that runs cold and soots up the plugs, or one that heats up the tell tale but never holds temperature.
Renewing the thermostat without the seal and the housing gasket is a false economy: the old gasket leaks, air enters the cooling system and the new thermostat reads the wrong temperature. This kit is the thermostat and both sealing parts for one job.
Specifications
| Specification | Detail |
|---|---|
| Condition | New / New with tags |
| Type | Outboard thermostat kit |
| Fits | Yamaha 9.9 and 15 HP two stroke |
| Years | 1984 to 2017 |
| Kit Contents | Thermostat, thermostat seal, housing gasket |
| Net Weight | 76 g including packaging |
| Pack Size | 15 x 10 x 3 cm |
| Quantity | One kit per engine |
OEM Cross Reference
| Brand | OEM Part Numbers |
|---|---|
| Yamaha | 6E5-12411-30 |
| Yamaha, earlier | 6E5-12411-20-00 |
| Yamaha, earlier | 6E5-12411-10-00 |
| Yamaha, earlier | 688-12411-00-00 |
| Yamaha, earlier | 688-12411-01-00 |
| Yamaha, earlier | 688-12411-10-00 |
| Yamaha, earlier | 688-12411-11-00 |
| Yamaha, earlier | 688-12411-01 |
| Mallory | 9-43035 |
| Sierra | 18-3540 |
Compatible Engines
| Model | Horsepower | Stroke | Years |
|---|---|---|---|
| Yamaha 9.9F | 9.9 HP | Two stroke | 1984 to 2017 |
| Yamaha 15F | 15 HP | Two stroke | 1984 to 2017 |
| Tiller models | 9.9 HP | Two stroke | 1984 to 2017 |
| Remote models | 15 HP | Two stroke | 1984 to 2017 |
| Electric start models | 9.9 and 15 HP | Two stroke | 1984 to 2017 |
| Manual start models | 9.9 and 15 HP | Two stroke | 1984 to 2017 |
What's Included
| Component | Detail | Qty |
|---|---|---|
| Outboard thermostat | 6E5-12411-30 pattern | 1 |
| Thermostat seal | Included, number not listed | 1 |
| Thermostat housing gasket | Included, numbers not listed | 1 |
| Housing and bolts | Not included, reuse the originals | 0 |
Cold Running and Overheating
| What You See | What It Means | What To Do |
|---|---|---|
| Motor never reaches temperature | Thermostat stuck open | Renew the thermostat |
| Tell tale weak, motor hot at speed | Thermostat stuck closed | Renew before the powerhead suffers |
| Plugs soot up quickly | Motor running cold all the time | Thermostat stuck open, renew the kit |
| Temperature climbs then drops | Thermostat cycling, weak spring | Renew the kit |
| Overheat alarm at low speed only | Restricted bypass, thermostat partly stuck | Renew and flush the cooling passages |
| Water in the cowl after a run | Housing gasket failed | Renew the gasket, this kit includes it |
Fitting Notes
| Step | Action |
|---|---|
| 1 | Check the number on the old thermostat, 6E5-12411-30 covers the 9.9F and 15F |
| 2 | Flush the motor on muffs before starting, a cold motor is easier to work on |
| 3 | Drain the cooling system and remove the thermostat housing cover |
| 4 | Clean both faces of the housing, old gasket left behind causes the next leak |
| 5 | Fit the thermostat with the bleed hole or jiggle pin at the top, as it came out |
| 6 | Fit the new seal and the housing gasket dry, no sealant |
| 7 | Tighten the cover evenly and refill the cooling system |
| 8 | Run on muffs and check the tell tale and the temperature before the next trip |
Condition & Warranty
| Item | Detail |
|---|---|
| Condition | New / New with tags |
| Warranty | Standard |
| Packaging | Sealed retail packaging |
Before You Buy
- Check the number on the old thermostat, 6E5-12411-30 and 688-12411-00-00 interchange
- Fits Yamaha 9.9F and 15F two stroke outboards from 1984 to 2017
- Also crosses to Mallory 9-43035 and Sierra 18-3540
- The kit includes the thermostat, the seal and the housing gasket
- Fit the bleed hole at the top, a thermostat fitted upside down will not open
- Clean both housing faces before fitting, or the new gasket will leak
- 30-Day Easy Returns
- Ships from our warehouse with tracking
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Boat Owners' Review
Before You Buy
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