Propeller Guards
The term “propeller guard” is a widely misused term since there are basically four types of propeller guards avaiable today. Each “guard” has its own listing of pros and cons. The various types and some of their advantages and disadvantages are below.

Deflection Type (Skegs)
These devices (basically prongs forward of the propeller) have been to protect the “motor and whatever it hits”. These provide some entry protection from ahead but provide no radial or astern protection. They sigificantly increase the potential for blunt trauma at higher speeds and also increase the potential for entanglement. They may also block the propeller movement if dented inward by floating debris or submerged objects.

Full Cages
There are a number of these devices all of which depend on some type of metal cage surrounding the propeller to prevent human entry to the propeller blades. These devices provide complete entry protection from the propeller but introduce a slightly increased risk of entaglement in the metal mesh. Because they are larger than the propeller and present a larger frontal area under the boat they increase the potential for blunt trauma injury at higher speeds. They are more easily fouled than a normal propeller in the presence of seaweed or debris and block the propeller movement if dented inward by floating debris or submerged objects. They may also cause cavitation significant enough to cause a loss of maneuverability when on a plane.

Shrouds or Ring Guards
These are a short cylinder surrounding the propeller which has an inside diameter slightly greater then the propeller diameter. These devices provide protection from radial entry into the propeller but limited protection fore and aft with an increased potential for limb entrapment when entered for and aft. Because they are larger than the propeller and present a larger frontal area under the boat they increase the potential for blunt trauma injury at higher speeds. They also are more easliy fouled than a normal propeller in the presence of seaweed or debris and bloak the propeller movement if dented inward by floating debris or submerged objects.