Four-Blade FX4 Turbo Prop By Yamaha is designed for midrange outboards. Improved bow and stern lift, Faster Acceleration, and load-carrying ability for 3 and 4-cylinder Outboards; The 4-blade design with a more aggressive pitch and high rake angle blade, provides quick acceleration and reduces steering torque. Excellent for 15-20' boats using 70 -130hp, 3 and 4-cylinder outboards with 4.25” gearcases. Works well on many smaller boats and applications.