Sierra 18-3609 Thermostat Kit for Yamaha 2-Stroke Outboards, OEM 6J8-12414-A0-00, 60 Degrees C

The Sierra 18-3609 Thermostat Kit is a complete cooling system replacement kit built for Yamaha 2-stroke outboard engines. Rather than sourcing a thermostat and gasket separately, this kit bundles both components so the cooling system can be serviced in a single step. It is engineered to meet or exceed the performance of the original equipment part it replaces, giving boat owners a dependable way to restore proper engine temperature regulation.

Inside the kit is one 18-3541 thermostat, cross-referenced to Yamaha OEM number 66M-12411-01-00, and one 18-0835 cover gasket, cross-referenced to Yamaha OEM number 62Y-12414-00-00. Together these components correspond to the Yamaha OEM kit equivalent 6J8-12414-A0-00. The thermostat is rated to open at 60 degrees C, matching the factory-specified opening temperature for the cooling systems this kit is designed to service.

A worn or stuck thermostat is a common cause of an overheating outboard, and the included gasket ensures a proper seal is restored at the same time the thermostat is replaced, preventing coolant leaks and repeat labor. This kit is intended for Yamaha 2-stroke outboard cooling systems.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3609
• Product Type: Thermostat Kit
• Temperature Rating: 60 degrees C
• Kit Contents: (1) 18-3541 Thermostat, (1) 18-0835 Cover Gasket
• Thermostat OEM Cross Reference: 66M-12411-01-00
• Gasket OEM Cross Reference: 62Y-12414-00-00
• Kit OEM Cross Reference: 6J8-12414-A0-00
• Engine Type: 2-Stroke
• Application: Yamaha Outboard Cooling System
• Weight: 0.09 pounds

Fitment

• Yamaha 2-stroke outboard cooling systems

Replaces (OEM)

• 6J8-12414-A0-00
• 66M-12411-01-00
• 62Y-12414-00-00

Frequently Asked Questions

What does the Sierra 18-3609 thermostat kit include? The kit includes one 18-3541 thermostat and one 18-0835 cover gasket, giving you both parts needed to service a Yamaha 2-stroke outboard cooling system in a single purchase.

What temperature does the 18-3609 thermostat open at? The thermostat included in the Sierra 18-3609 kit is rated to open at 60 degrees C, which matches the factory cooling system specification it is designed to service.

Is the Sierra 18-3609 an OEM-equivalent part? Yes. The Sierra 18-3609 kit cross-references to Yamaha OEM kit number 6J8-12414-A0-00, with the individual thermostat matching OEM number 66M-12411-01-00 and the gasket matching OEM number 62Y-12414-00-00.

Which engines is the 18-3609 thermostat kit designed for? This kit is designed for Yamaha 2-stroke outboard cooling systems.

Do I need to replace the gasket along with the thermostat? Yes, replacing both together is recommended, which is why the 18-3609 kit bundles the 18-3541 thermostat with the 18-0835 cover gasket rather than selling the thermostat alone.

How much does the 18-3609 thermostat kit weigh? The Sierra 18-3609 thermostat kit weighs 0.09 pounds.

What OEM part numbers does the 18-3609 kit replace? The 18-3609 kit corresponds to Yamaha OEM numbers 6J8-12414-A0-00 (kit), 66M-12411-01-00 (thermostat), and 62Y-12414-00-00 (gasket).

Can a failed thermostat cause my outboard to overheat? A stuck or worn thermostat is a common cause of outboard overheating, which is why the 18-3609 kit is designed to restore correct temperature regulation with a fresh, properly rated 60 degree C thermostat.

Does Sierra manufacture this part to OEM standards? Sierra products, including the 18-3609 kit, are engineered to meet or exceed the performance of the original equipment part they replace.

Is the 18-3609 a two-stroke or four-stroke application? The Sierra 18-3609 thermostat kit is built for Yamaha 2-stroke outboard cooling systems.