Sierra 18-3553 Brass Thermostat, 143 Degree F, Replaces Mercury 75692, Fits Mercury V135/V150

The Sierra 18-3553 is a brass thermostat built for Mercury marine engine applications. It is manufactured to control engine operating temperature at a 143 degree F rating, matching the original equipment part it replaces. The brass construction is chosen for corrosion resistance and reliable, consistent operation in a marine cooling system where saltwater and freshwater exposure can degrade lesser materials over time.

This thermostat directly replaces Mercury Marine part number 75692 and is engineered to meet or exceed the performance of the original equipment component it is designed to replace. It fits Mercury V135 and V150 series engines, including the V150 XR4, V150 XR6, and V150 MAGII variants, within the serial number ranges listed below. Confirming your engine's serial number against these ranges before ordering will help ensure correct fitment.

Sierra is a long-established supplier of marine replacement parts, and this thermostat is covered under Sierra's standard customer satisfaction warranty. It is a straightforward drop-in replacement for engine cooling system maintenance and repair.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3553
• Product Type: Thermostat
• Material: Brass
• Temperature Rating: 143 degrees F
• Weight: 0.06 pounds
• OEM Cross Reference: 75692
• UPC: 030999236913
• Fitment: Mercury V135, V150, V150 XR4, V150 XR6, V150 MAGII

Fitment

• Mercury V135, serial number A904646 and up
• Mercury V150, serial number A904646 and up
• Mercury V150 XR4, serial number C239553 to C159199
• Mercury V150 XR6, serial number D082000 and up
• Mercury V150 MAGII, serial numbers C239553, 4571651

Replaces (OEM)

• 75692

Frequently Asked Questions

What engines does the Sierra 18-3553 thermostat fit? The Sierra 18-3553 thermostat fits Mercury V135 and V150 series engines, including the V150 XR4, V150 XR6, and V150 MAGII, within specific engine serial number ranges, so it is best to confirm your engine's serial number before ordering.

What temperature rating is the 18-3553 thermostat? It is rated at 143 degrees F, which is the temperature at which the thermostat opens to allow coolant flow through the engine.

What OEM part number does the Sierra 18-3553 replace? This thermostat replaces Mercury Marine OEM part number 75692.

What material is the Sierra 18-3553 thermostat made from? Brass is the material used for the Sierra 18-3553 thermostat, chosen for its corrosion resistance in marine cooling systems.

How much does the Sierra 18-3553 thermostat weigh? The Sierra 18-3553 thermostat weighs 0.06 pounds.

Is the Sierra 18-3553 a genuine Mercury Marine part or an aftermarket replacement? It is a Sierra-brand aftermarket thermostat manufactured to meet or exceed the performance of the original Mercury Marine 75692 part it replaces, not a Mercury Marine branded part.

Does the Sierra 18-3553 thermostat include a gasket? No, the Sierra 18-3553 is the thermostat itself; the thermostat gasket is a separate Sierra part number and should be ordered individually if needed.

What serial number range applies to the V150 XR4 engine for this thermostat? For the Mercury V150 XR4, the Sierra 18-3553 thermostat applies to engine serial numbers from C239553 to C159199.

What is the UPC for the Sierra 18-3553 thermostat? The UPC for the Sierra 18-3553 thermostat is 030999236913.

Is the Sierra 18-3553 thermostat covered by a warranty? Yes, the Sierra 18-3553 thermostat is covered under Sierra's standard customer satisfaction warranty.