Would a 4 blade boat prop be faster than a 3 blade prop?

Answer 1

Which propeller to choose?3 blade props are the most common, come in the widest variety of styles and sizes and will typically cost less than a comparable 4 blade prop. Switching from a 3 blade propeller to a 4 blade propeller may make sense for you if you are trying to improve your hole shot or low-end torque for pulling wake boarders, skiers or tubes. It might also make sense if you typically run at mid-range RPMs and are looking for improved fuel economy. How Come?Geometry:This refers to the design aspects of a propeller similar to blade shape and size, pitch angles, cupping and rake. 3 blade boat props come in a variety of designs ranging from general purpose styles like the Quicksilver Silverado or Solas Saturn to more specialized designs for heavy boats or extreme speed and performance like the Solas Scorpion.

On the other hand, 4 blade props are typically designed to capitalize on hole shot, pulling power and mid-range performance.

Blade Prop Area: If you took 2 propellers that are the same design except for the number of blades, the 3 blade prop will typically have larger blades, but the 4 blade prop will have more total blade area. The increased blade area will allow the 4 blade prop to displace more water. It will also have more drag which can contribute to a slightly slower top end speed. The additional drag and displacement means it takes more power to turn a 4 bladed prop. The general rule of thumb is to drop 1" - 2" of pitch if you are moving from a 3 blade prop to a 4 blade propeller, assuming you were at optimum RPMs with the 3 blade prop. The decrease in pitch will increase the RPMs, offsetting any decrease in RPMs that would arise from the 4 blade configuration, allowing you to maintain optimal engine rev.

Stern Lift and Ventilation: The design and weight of the motor in the stern causes some boats to squat in the water. A 4 blade prop produces more stern lift which can help these boats run in better trim and attain a plane more quickly. A lot stern lift can cause some boats to ride too high in the stern leading to ventilation issues, where the prop pulls air, thereby decreasing thrust and increasing RPMs. When ventilation occurs, or if a prop is prone to slipping during hard turns, the greater blade surface in contact with the water with a 4 blade prop means that it will often perform better than a 3 blade prop under those conditions.

The ultimate decision of whether to go with a 3 blade or 4 blade prop comes down to your boat's performance and what you want to accomplish. Taking all of these factors into consideration will help you in making your decision. Please feel free to contact us if we can assist you with selecting the best prop for your boating style.