Sierra 18-3555 Thermostat, 160 Degree, for Mercruiser 7.4L MIE 454 V-8 Closed Cooling 1996-1997

The Sierra 18-3555 is a 160 degree marine thermostat engineered for Mercruiser 7.4L MIE 454 cubic inch V-8 stern drive engines equipped with closed (fresh water) cooling. It mounts at the engine block and regulates coolant flow through the closed cooling loop, opening at 160 degrees Fahrenheit to keep the engine operating in its correct temperature range for efficient combustion and reduced wear. The thermostat is finished in white and installs using the standard engine block mount configuration found on this Mercruiser engine family. It is built to meet or exceed the performance of the original equipment component it replaces, making it a straightforward like-for-like replacement for a worn, stuck, or failed thermostat. This part is specific to the 7.4L EFI MIE 454 V-8 configuration with closed cooling covering the 1996-1997 model years and the serial number range noted in the fitment section below, so confirm your engine's cooling system type and serial number before ordering. Keeping the thermostat within spec protects against overheating and helps the engine reach efficient operating temperature faster after startup.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3555
• Temperature Rating: 160 degrees Fahrenheit
• Cooling System Type: Closed Cooling (Fresh Water Cooling)
• Color: White
• Mounting Type: Engine Block Mount
• Weight: 0.07 pounds
• UPC: 030999316035

Fitment

• Mercruiser MIE 7.4L EFI 454 cubic inch V-8, Closed Cooling, 1996-1997, serial numbers F874815 through K999999

Replaces (OEM)

• GLM 13040
• Mallory 9-43001
• Mallory 9-43016
• Mercruiser Stern Drive 991551
• Mercruiser Stern Drive 99155A1
• Mercruiser Stern Drive 99155T2

Frequently Asked Questions

What temperature does the Sierra 18-3555 thermostat open at? The Sierra 18-3555 is rated to open at 160 degrees Fahrenheit, which is the standard operating temperature for the Mercruiser closed cooling systems it is designed for.

Which engines does the 18-3555 thermostat fit? This thermostat fits Mercruiser MIE 7.4L EFI 454 cubic inch V-8 engines with closed cooling, covering the 1996-1997 model years within serial number range F874815 through K999999.

Does the 18-3555 work on standard raw water cooled engines? No. The 18-3555 is built for the closed (fresh water) cooling version of the Mercruiser 7.4L EFI MIE 454 V-8; engines with standard raw water cooling use a different Sierra thermostat.

What OEM part numbers does the Sierra 18-3555 cross-reference? The 18-3555 interchanges with GLM 13040, Mallory 9-43001 and 9-43016, and Mercruiser Stern Drive 991551, 99155A1, and 99155T2.

Is the Sierra 18-3555 a genuine Mercruiser part or aftermarket? The 18-3555 is a Sierra aftermarket thermostat manufactured to meet or exceed the performance of the original Mercruiser equipment it replaces, not a Mercruiser-branded part.

How much does the 18-3555 thermostat weigh? The Sierra 18-3555 thermostat weighs 0.07 pounds.

What color is the 18-3555 thermostat? The 18-3555 has a white finish.

How does the 18-3555 mount to the engine? It uses an engine block mount configuration, installing directly at the engine block on the closed cooling loop of the Mercruiser 7.4L MIE 454 V-8.

What is included when I order the 18-3555? The listing includes one Sierra 18-3555 160 degree marine thermostat.

Why would I replace my thermostat with the 18-3555? A stuck, corroded, or out-of-spec thermostat can cause a Mercruiser 7.4L MIE 454 V-8 to run too hot or too cold; the 18-3555 restores the correct 160 degree opening point for the closed cooling system.

Is there a UPC for the Sierra 18-3555? Yes, the Sierra 18-3555 thermostat carries UPC 030999316035.