Yamaha - Vapor Separator Tank Fuel System 68V-13915-00-00. Overview. The Yamaha 68V-13915-00-00 VST Filter plays a critical role in protecting the fuel injection system of Yamaha outboard engines. Located inside the Vapor Separator Tank (VST), this filter removes fine contaminants from fuel before it reaches the high-pressure fuel pump and fuel injectors. Clean fuel is essential for proper combustion, smooth throttle response, and reliable engine performance. Replacing the VST filter as part of