From iboats:
3 blades... or 4?
We recommend 3-blade propellers for recreational boats with 3, 4, and 6 cylinder outboards and I/0 engines.
3-blades provide good "hole shot" and top-speed performance.
We recommend 4-blade propellers for bass boats and those with high performance hulls running high horsepower outboard engines.
Compared to 3 blades, 4-blade boat props provide better "hole shot" performance with less steering torque and less vibration at high speeds.
When switching from 3 to 4-blades, generally a 1" pitch decrease is required. So, a 21" pitch 3-blade is replaced with a 20" pitch 4-blade. Pitch is increased when switching from 4 to 3-blades.
