Mercury-MerCruiser 991551T1 160°F Thermostat Kit

The Mercury-MerCruiser 991551T1 Thermostat Kit is designed for 1998 and newer MerCruiser marinized V6 and V8 engines made by General Motors that use closed cooling systems and require a 160°F thermostat. This kit includes the thermostat and seal needed for replacement during cooling system service.

A properly functioning thermostat helps regulate engine operating temperature and supports reliable cooling system performance. Replacing a worn, stuck, or non-functioning thermostat can help restore proper temperature control in compatible MerCruiser applications.

Product Features:

• 160°F thermostat kit for compatible MerCruiser applications
• Designed for 1998 and newer GM V6 and V8 MerCruiser marinized engines
• For engines using closed cooling systems that require a 160°F thermostat
• Includes thermostat and seal
• Can be replaced with common tools
• Manufactured to Mercury Marine OEM specifications

Product Details:

• Brand: Mercury / MerCruiser
• Manufacturer Part Number: 991551T1
• Part Type: Thermostat Kit
• Temperature Rating: 160°F
• Cooling System Type: Closed cooling
• Engine Application: 1998 and newer GM V6 and V8 MerCruiser marinized engines
• Includes: Thermostat and seal

Installation Note: Refer to your owner’s manual or service manual for removal of the non-functioning thermostat and installation of the replacement thermostat.

Fitment Note: This thermostat kit is for compatible MerCruiser GM V6 and V8 engines with closed cooling systems requiring a 160°F thermostat. Please verify fitment by engine serial number, cooling system type, parts diagram, or existing part number before purchasing.

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