Before we begin to list the actual steps that one must take to determine the size of boat props, let us discuss the 2 primary players in the boat prop measuring world. They go by the name of diameter and pitch. These numbers go together like water and boats, marinas and money, and fish and water. The two elements that you always want to be aware of are the diameter of the prop, as well as the pitch of the boat prop. For example, if a boat propeller has a pitch of 24" and a diameter of 10, is would be known as a "10/24" propeller. The best place to find out what kind of boat propeller that you have is to look at the hub of the boat prop. This information is usually written conveniently on the hub of the boat propeller. Unluckily, because of the erosion that has taken place because of water, constant use, and other mitigating circumstances this number may no longer be visible. Also, if the person who owned the boat before you did had a propeller that was unique, this information can be next to impossible to find.