The most common error is to install a propeller of too large a diameter for the power available. Like a screw turning into a piece of wood, the pitch of a propeller is the distance it will advance in one revolution through the water, assuming there is no slippage. There are two kinds of slip. Apparent slip is the difference between the advance observed and that calculated by pitch times revolutions. It is what is more important.
True slip is greater than apparent slip, due to wake moving with the vessel.
The wake that affects slip is a body of water surrounding the propeller and moving along with the vessel. The amount of wake is determined by the amount of friction produced by the hull moving through the water. Find apparent slip, knowing the vessel speed, revolutions, and propeller pitch. Material it was made out of. Disturbances are easily created by posts not faired, struts too close.