Sierra Thermostat 18-3525 for Yamaha 2-Stroke Outboards VZ200, V225, VZ250

The Sierra 18-3525 is a replacement cooling system thermostat engineered for Yamaha 2-stroke outboard engines. It regulates engine operating temperature by controlling coolant flow through the cooling system, helping the engine reach and maintain proper running temperature for efficient performance and long-term reliability. This thermostat is a direct application-specific part for the Yamaha VZ200 (2005-09), V225 (2003-09), and VZ250 (2003-09) outboards, and each of these engines requires two thermostats per engine for complete cooling system coverage.

As a cooling system wear item, the thermostat should be inspected and replaced as part of routine outboard maintenance or whenever overheating, erratic temperature gauge readings, or reduced engine performance point to a stuck or failing thermostat. Installing the correct application-specific thermostat is important, since Yamaha 2-stroke outboards use different Sierra thermostat part numbers depending on model and year.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3525
• Product Type: Thermostat
• Engine Type: Yamaha 2-Stroke Outboard
• Quantity Per Engine: 2
• Color: Copper
• Weight: 0.11 pounds
• UPC: 808282339364

Fitment

• Yamaha VZ200, 2005-09
• Yamaha V225, 2003-09
• Yamaha VZ250, 2003-09

Replaces (OEM)

• No OEM cross-reference numbers listed for this part number.

Frequently Asked Questions

What does the Sierra 18-3525 thermostat do? It regulates coolant flow in the cooling system of a Yamaha 2-stroke outboard so the engine reaches and holds its proper operating temperature. Part number 18-3525 is the Sierra replacement thermostat for this application.

Does the Sierra 18-3525 fit a Yamaha VZ200 outboard? Yes, thermostat 18-3525 is the listed application for the Yamaha VZ200 covering model years 2005-09.

Which Yamaha outboard models use thermostat 18-3525? Thermostat 18-3525 applies to the Yamaha VZ200 (2005-09), V225 (2003-09), and VZ250 (2003-09).

How many thermostats does my Yamaha 2-stroke outboard need? Two. The VZ200, V225, and VZ250 applications for the Sierra 18-3525 each require a quantity of 2 thermostats per engine.

Is a gasket included with the Sierra 18-3525 thermostat? No separate gasket or thermostat kit number is listed for part 18-3525, so it is supplied as the thermostat only.

What is the weight of the Sierra 18-3525 thermostat? It weighs 0.11 pounds.

Will 18-3525 fit a Yamaha V225 from 2003 to 2009? Yes, the V225 model years 2003-09 use thermostat 18-3525, with two units required per engine.

What years does the VZ250 application cover for part 18-3525? The Yamaha VZ250 application for thermostat 18-3525 covers model years 2003-09.

How is 18-3525 different from the Sierra 18-3540 thermostat? 18-3525 is the thermostat for the Yamaha VZ200 (2005-09), V225 (2003-09), and VZ250 (2003-09), while 18-3540 is a separate part number used on other Yamaha 200-250 hp applications and comes with its own matching gasket and kit numbers. The two are not interchangeable across applications.

Is the Sierra 18-3525 a genuine Yamaha part or aftermarket? Sierra 18-3525 is an aftermarket replacement thermostat manufactured by Sierra for the specified Yamaha 2-stroke outboard applications.

How do I know if my outboard's thermostat needs replacing? Signs include engine overheating, erratic temperature gauge readings, or reduced cooling performance; on the applicable Yamaha VZ200, V225, or VZ250 outboards, the Sierra 18-3525 is the correct replacement thermostat to install.