The obvious function of the barrel, or outer hub, of a propeller is to be the attachment point for the propeller blades. What is often overlooked, however, is that the length, diameter and shape a propeller barrel can have a direct effect on boat performance.
Mercury Racing propellers currently have three barrel sizes. The smallest-diameter barrel is found on solid-hub props with broached splines like the Mercury Racing CNC Cleaver model. Barrels also come in different lengths and some have a flared trailing edge.
Mercury Racing offers different barrel lengths and shapes on the Bravo I, Maximus, and MAX5 propeller families. The longer and wider the barrel, the more stern lift the propeller will generate. Adding flare to the aft end of the barrel also generates stern lift; a long barrel with a flare acts as a miniature trim tab, providing lift and improving hole shot. This is why, for example, the Mercury Racing Bravo I XC has a longer barrel with a flared trailing edge – both features help fishing boats used in the Texas Gulf Coast market plane off quickly in very shallow water, and hold plane at lower speeds as anglers sight fish.