Sierra 18-3649 160 Degree Thermostat, Replaces Mercury Marine 807252-2, Fits Mercruiser 4.3L/4.3LX (262 CID)

The Sierra 18-3649 is a 160 degree F thermostat built for Mercruiser 205/4.3L and 4.3 LX (262 CID) sterndrive engines with serial number F001220 and up. It is designed for engines using a single and 3-point drain cooling system, and it regulates coolant flow so the engine reaches and holds its correct operating temperature. The thermostat is a direct replacement for the original equipment unit on this engine and serial range, restoring proper warm-up and temperature control when the factory thermostat has failed, is stuck open or closed, or is simply due for routine replacement.

This thermostat cross-references to OEM and aftermarket numbers used across several marine engine brands, including Crusader, GLM, Mallory, and Mercury Marine/Mercruiser part numbers, making it a straightforward swap for boat owners and marine technicians replacing a worn or failed thermostat. Confirm your engine's serial number falls within the F001220 and up range before ordering, since Sierra lists a different thermostat (18-3668) for earlier engines in the same 205/4.3L, 4.3 LX (262 CID) model line.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3649
• Temperature Rating: 160 degrees F
• Product Dimensions: 5 inches D x 4 inches W x 1 inch H
• Weight: 0.13 pounds
• UPC: 808282258832
• Fitment: Mercruiser 205/4.3L, 4.3 LX (262 CID) engines, serial number F001220 and up
• Drain System: Single and 3-point drain system
• OEM Cross Reference: Crusader 97895, GLM 13100, Mallory 9-43002, Mercury Marine 807252-2, Mercruiser 8M0091470, 807252T2, 8072522, 8052732, 8M0109441

Fitment

• Mercruiser 205/4.3L, 4.3 LX (262 CID) engines, serial number F001220 and up

Replaces (OEM)

• Crusader 97895
• GLM 13100
• Mallory 9-43002
• Mercury Marine 807252-2
• Mercruiser 8M0091470
• Mercruiser 807252T2
• Mercruiser 8072522
• Mercruiser 8052732
• Mercruiser 8M0109441

Frequently Asked Questions

What temperature does the Sierra 18-3649 thermostat open at? The Sierra 18-3649 is rated at 160 degrees F, which is the temperature at which it begins to open and allow coolant to circulate.

Which engines does the Sierra 18-3649 fit? This thermostat fits Mercruiser 205/4.3L and 4.3 LX (262 CID) engines with serial number F001220 and up, and is intended for engines using a single and 3-point drain cooling system.

Does the Sierra 18-3649 fit earlier 4.3L Mercruiser engines below serial number F001220? No. Earlier 205/4.3L, 4.3 LX (262 CID) engines below serial number F001220 use a different Sierra thermostat, 18-3668, so check your engine's serial number before ordering 18-3649.

What OEM part numbers does the Sierra 18-3649 replace? It cross-references to Crusader 97895, GLM 13100, Mallory 9-43002, Mercury Marine 807252-2, and Mercruiser 8M0091470, 807252T2, 8072522, 8052732, and 8M0109441.

How much does the Sierra 18-3649 thermostat weigh? The Sierra 18-3649 thermostat weighs 0.13 pounds.

What are the dimensions of the Sierra 18-3649? It measures 5 inches deep by 4 inches wide by 1 inch high.

Is the Sierra 18-3649 a genuine OEM part or aftermarket? The 18-3649 is a Sierra-branded replacement thermostat manufactured to meet or exceed the specifications of the original equipment part it replaces, rather than a Mercury Marine or Crusader branded OEM part.

What comes in the box with the Sierra 18-3649? The Sierra 18-3649 ships as a single thermostat unit.

Can the Sierra 18-3649 be used on a closed cooling system? The 18-3649 is listed for engines with a single and 3-point drain cooling system; confirm your engine's cooling configuration and serial number match before installing.

What is the UPC for the Sierra 18-3649 thermostat? The Sierra 18-3649 thermostat carries UPC 808282258832.

Why are there multiple cross-reference numbers listed for the Sierra 18-3649? Different engine and boat manufacturers, including Crusader, GLM, Mallory, and Mercury Marine, sold their own branded versions of the same thermostat, so the 18-3649 cross-references to each of their part numbers.

How do I know if I need the Sierra 18-3649 instead of a similar Sierra thermostat? Match your engine model (205/4.3L or 4.3 LX, 262 CID) and serial number to the F001220-and-up range specified for the 18-3649; engines outside that range require a different Sierra part number.