Skat-Trak’s Yamaha impeller is recommended with a 14/19 Swirl* or 13/18 Super Slim Line** pitch in any 144mm pump. This is recommended for a stock Engine only. If you have modification to the engine and watercraft, please give us a call so that we can recommend you with the correct impeller application. *Suggested for maximum bottom-to-mid range acceleration gains.**Sugested for maximum top speed gains.