NEW 991551 863358T 27-896561 THERMOSTAT FOR MERCRUISER STERNDRIVE 4.3L 5.7L 7.4L

Thermostat for MerCruiser

This thermostat for MerCruiser sterndrive engines replaces OEM part numbers 991551, 863358T, and 27-896561 to regulate engine temperature.

Overview

This thermostat for MerCruiser sterndrive engines ensures optimal operating temperature. The thermostat opens and closes to maintain proper cooling flow, preventing overheating or overcooling. For MerCruiser 4.3L, 5.7L, and 7.4L engines, this thermostat is a direct replacement part.

Built For Performance

• Precision-calibrated opening temperature for consistent operation
• Rugged construction for saltwater and freshwater use
• Compatible with multiple MerCruiser engine displacements
• OEM-spec replacement for part numbers 991551, 863358T, 27-896561

Fits These Machines

• for MerCruiser 4.3L
• for MerCruiser 5.7L
• for MerCruiser 7.4L

On-The-Job Use

• Replaces worn thermostats during cooling system service
• Ensures even engine warm-up in marine applications
• Helps maintain fuel efficiency and performance
• Used in both saltwater and freshwater boating

Specs At A Glance

Good To Know

Q: What is the typical opening temperature? A: Usually around 160°F, but check your engine's specification.

Q: Can this thermostat be used with raw water cooling? A: Yes, it is designed for marine cooling systems.

Slight variation in finish or dimensions may occur between production runs, and fit can depend on serial number, so confirm compatibility before ordering.