Sierra Thermostat Kit 18-3672, Fits Johnson/Evinrude 200 HP (1977-83) and 235 HP (1978-85) Outboards

This Sierra thermostat kit, part number 75-00456, is a direct replacement for outboard motor part 18-3672 and is built for owners who need to restore correct cooling system operation on Johnson/Evinrude (OMC/BRP) outboards. A thermostat regulates engine operating temperature by opening and closing to control coolant flow, and a worn, stuck, or corroded unit is a common cause of overheating or an engine that runs too cool, both of which reduce efficiency and can lead to premature wear. Replacing the thermostat with a properly sized unit restores the engine to its designed operating temperature range, helping protect internal components and keep fuel combustion efficient.

This kit is application-specific rather than a universal part, matching the thermostat used on Johnson/Evinrude 200 HP outboards from 1977-83 and 235 HP outboards from 1978-85. Confirming your engine's horsepower and model year against this fitment before ordering will ensure you get the correct thermostat for your motor. At 0.063 pounds, this is a small, lightweight component intended to be installed as part of routine cooling system maintenance or when troubleshooting an overheating condition.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 75-00456
• Replaces (OEM): 18-3672
• Weight: 0.063 pounds
• UPC: 840080484433
• Product Type: Outboard thermostat kit

Fitment

• Johnson/Evinrude (OMC/BRP) 200 HP outboards, 1977-83
• Johnson/Evinrude (OMC/BRP) 235 HP outboards, 1978-85

Replaces (OEM)

• 18-3672

Frequently Asked Questions

What does Sierra thermostat kit 75-00456 fit? This kit fits Johnson/Evinrude (OMC/BRP) outboards rated 200 HP from 1977-83 and 235 HP from 1978-85. Confirm your engine's horsepower and model year match before ordering.

Is 75-00456 the same as OEM part 18-3672? Yes, Sierra part 75-00456 is a direct replacement for OEM thermostat 18-3672 on the listed Johnson/Evinrude 200 HP and 235 HP outboard applications.

How much does this thermostat kit weigh? The Sierra thermostat kit, part 75-00456, weighs 0.063 pounds.

What is the UPC for this Sierra thermostat kit? The UPC for Sierra part 75-00456 is 840080484433.

Will this thermostat work on any outboard, or is it application-specific? Part 75-00456 is application-specific, not universal, and is built for Johnson/Evinrude 200 HP (1977-83) and 235 HP (1978-85) outboards only.

What are the signs I need to replace my outboard's thermostat? An engine that overheats, runs unusually cool, or has erratic temperature gauge readings often points to a failed thermostat; Sierra kit 75-00456 replaces the OEM 18-3672 unit on the applicable Johnson/Evinrude models.

Is this a genuine Sierra part or an aftermarket copy? This is a Sierra-branded thermostat kit, part number 75-00456, manufactured as a replacement for OEM part 18-3672.

Does the kit include the thermostat and gasket, or just the thermostat? This is listed as a thermostat kit under part number 75-00456; specific included components beyond the thermostat itself are not detailed further here.

Can I install this thermostat myself? Thermostat replacement on Johnson/Evinrude 200 HP and 235 HP outboards is a routine maintenance task that many owners perform themselves, though following your engine's service procedure is recommended when installing Sierra part 75-00456.

What horsepower and year ranges does OEM number 18-3672 cover? OEM thermostat 18-3672, replaced by Sierra kit 75-00456, covers Johnson/Evinrude 200 HP outboards from 1977-83 and 235 HP outboards from 1978-85.