Quicksilver 59078Q3 Replacement 140°F Thermostat Kit for MerCruiser Inline 4 & 6-Cylinder Engines

The Quicksilver 59078Q3 Replacement Thermostat Kit is an OEM-quality cooling system component designed for older MerCruiser inline 4-cylinder and 6-cylinder engines manufactured by General Motors. This kit provides a direct, reliable replacement for a worn or failed thermostat, helping maintain proper engine operating temperature and protecting your marine engine from overheating or running too cold.

As a Quicksilver product, the 59078Q3 is built to Mercury Marine's original equipment manufacturer specifications — ensuring a precise fit and dependable performance that aftermarket alternatives simply can't match.

Kit Contents & Specifications:

• 140°F thermostat — opens at the correct temperature for optimal engine performance
• Cork thermostat gasket included — complete 2-piece kit, no additional hardware needed
• Designed for older MerCruiser GM inline 4- and 6-cylinder stern drive engines
• Cross-references: 59078T3, 59078T4, Sierra 18-3650, Sierra 18-3550

Installation:

• Serviceable with common hand tools
• Refer to your engine's owner's manual or service manual for thermostat removal and installation procedures

Quicksilver is Mercury Marine's premier brand for original equipment replacement parts, oils, and accessories — trusted by marine technicians and boat owners for over 65 years. Choosing Quicksilver means choosing parts engineered and tested to the highest marine industry standards.