Sierra 18-3611 Thermostat Kit for Yamaha F15-F60, T9.9-T60 Outboards, Replaces 6E5-12411-30-00

The Sierra 18-3611 Thermostat Kit is a complete cooling-system repair kit for compatible Yamaha outboard engines, pairing a 140 degree F (60 degree C) thermostat with its matching gasket in one package. The thermostat regulates engine coolant flow to keep the powerhead within its designed operating temperature range, opening at 140 degrees F to allow water flow once the engine reaches operating temperature and helping prevent overheating or over-cooling that can accelerate wear on internal components. The included gasket seals the thermostat housing to prevent coolant leaks after installation. Sierra engineers this kit to meet or exceed the specifications of the original equipment parts it replaces, and Sierra supplies OEM engine manufacturers and boat builders with parts on a daily basis, so the fit and function match what the engine was originally designed around. This kit fits a broad range of Yamaha outboard models, including the 15, F15, F25, F30, F40, F50, F60, F9.9, T25, T50, T60, and T9.9. Because thermostat failure is a common cause of overheating alarms and inconsistent engine temperature, replacing both the thermostat and gasket together, as this kit allows, is the recommended approach rather than reusing an old gasket. The kit is a straightforward maintenance item for routine cooling system service or as a repair when overheating symptoms appear.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3611
• Product Type: Thermostat Kit
• Thermostat Temperature Rating: 140 degrees F / 60 degrees C
• Kit Contents: 1 thermostat (Sierra 18-3540), 1 gasket (Sierra 18-0844)
• Weight: 0.08 pounds
• UPC: 808282265540

Fitment

• Yamaha 15 (2006)
• Yamaha F15 (1998-06)
• Yamaha F25 (1999-06)
• Yamaha F30 (2001-06)
• Yamaha F40 (1999-06)
• Yamaha F50 (1996-06)
• Yamaha F60 (2002-06)
• Yamaha F9.9 (2005-06)
• Yamaha T25 (2001-06)
• Yamaha T50 (1996-06)
• Yamaha T60 (2003-06)
• Yamaha T9.9 (2005-06)

Replaces (OEM)

• 6E5-12411-30-00 (thermostat)
• 688-12414-A1-00 (gasket)

Frequently Asked Questions

What temperature does the Sierra 18-3611 thermostat open at? It opens at 140 degrees F (60 degrees C), which is the temperature rating specified for the thermostat included in the Sierra 18-3611 kit.

What is included in the 18-3611 kit? The kit contains one thermostat and one matching gasket, so you can replace both parts together during a single service on compatible Yamaha outboards.

Which Yamaha outboard models does the 18-3611 thermostat kit fit? It fits the Yamaha 15 (2006), F15 (1998-06), F25 (1999-06), F30 (2001-06), F40 (1999-06), F50 (1996-06), F60 (2002-06), F9.9 (2005-06), T25 (2001-06), T50 (1996-06), T60 (2003-06), and T9.9 (2005-06).

Does this kit include the gasket, or do I need to buy it separately? The gasket is included in the Sierra 18-3611 kit along with the thermostat, so no separate gasket purchase is needed for a standard replacement.

What OEM part numbers does the Sierra 18-3611 kit replace? The kit's components correspond to OEM numbers 6E5-12411-30-00 for the thermostat and 688-12414-A1-00 for the gasket.

Is the Sierra 18-3611 an OEM part or an aftermarket equivalent? It is an aftermarket kit manufactured by Sierra, engineered to meet or exceed the specifications of the original equipment thermostat and gasket it replaces.

How much does the 18-3611 thermostat kit weigh? The complete kit weighs 0.08 pounds.

Will this thermostat kit fit a Yamaha F50 outboard? Yes, the Sierra 18-3611 kit is listed as fitting the Yamaha F50 for model years 1996 through 2006.

When should the thermostat and gasket be replaced? Both parts in the 18-3611 kit are typically replaced together whenever the thermostat is serviced, since the gasket should not be reused once the housing has been opened.

What is the UPC for the Sierra 18-3611 kit? The UPC is 808282265540.

Does the kit fit the Yamaha T9.9 outboard? Yes, the Sierra 18-3611 thermostat kit lists compatibility with the Yamaha T9.9 for model years 2005 through 2006.

What brand manufactures the 18-3611 thermostat kit? Sierra manufactures the 18-3611 thermostat kit.