In order for your boat propeller to work at its maximum potential, it must be free from any additional substances that may collect on it. Since modern propellers are usually made from stainless steel, bronze or a Nibral alloy (nickel, brass or aluminum), they are resistant to corrosion, yet any growth from the aquatic environment such as slime, moss or mussels that can grow in freshwater or barnacles from saltwater must be cleaned off. A new or properly cleaned propeller goes a long way to preventing propeller unbalance, created uninterrupted laminar flow over the blades as well as making the best use of the power of the bow thrusters system.
E-How has these provides the following guide on cleaning your propeller:
1. Remove the cotter pin from your boat’s propeller shaft with pliers (needlenose) and break the torque on the locknut with the breaker bar and socket. The locknut can be taken off by hand and the locknut itself, the washer and propeller can be removed from the shaft.
2. Any mussels or barnacles can be removed with a chisel, but be careful not to create dents or gouge the propeller. All traces of barnacles should be removed. If there are any barnacle bases still attached, remove them with a wire brush and pressure wash slime or hair off.
3. The wheel should be inspected for nicks and dents. Any nicks or cuts in the edges of the blades should be filed down so that they cannot cause drag with the machine file.
4. The prop should be sanded with a rotary sander or a 180-grit paper. Note that the sandpaper will clog up frequently, as this is the case with bronze and Nibral props. Corrosion and pitting should be sanded out until the entire propeller has a uniform and shiny.
Note that unless you are experienced with dealing with extremely pitted or used propellers, they should be sent to a professional to be refinished, balanced or even replaced. Using an unbalanced prop will cause bow thruster systems, cutlass bearings and drive-train components to wear down quickly. It not done properly, vibration may cause the stuffing box to leak, possibly causing flooding and engine damage.