I am always asked why should I have a 2, 3, or 4 blade propeller on my boat. The answer truly comes down to how you use the boat.
If you primarily use the engine to power in and out of the marina or when the wind dies a two blade is a great choice. Or if your primary use of the boat is to race. As a two blade will have less drag than a 3 blade, while not much more drag, there is more drag in your mind and you will use it as an excuse as to why the boat is going slow.
If you use your boat for cruising, or if you have to power in to a current every time you go out a 3 or 4 blade is the better choice. They have a major advantage when going against heavy winds and seas or a current as they will keep your boat speed by up to 30% better than the two blade. Moreover, they will run much smoother and reduce vibrations as it is balanced around 3 or 4 points as opposed to 2.
A 4 blade is a great choice if the vessel is heavy for its length the increased blade area will power the boat more efficiently. Or there is a limitation in the size of propeller the vessel will fit a 4 blade will allow for a more efficient pitch. Also fast shaft Rpm, if the shaft rotates at above 1500 rpm the 4 blade will smooth out annoying vibrations. Another reason for installing a 4 blade is when the vessel has limited horsepower. For example a 50’ boat with a 75 horsepower engine, the 4 blade will have the much needed blade area to keep the vessel powering into heavy wind an seas.