There is no doubt that the propeller is one of the most important factors that can make great difference in our boat's performance. Knowing the parts of the propeller, we will be better able to understand how a propeller works and going a little bit further by knowing its basic features, we will be able to choose the most suitable one for our needs.
The hub of a propeller is the “center round barrel” to which the propeller blades are attached.
On “through-hub exhaust propellers” we distinguish the Outer and the Inner Hub which are connected together by the Ribs. In these propellers the engine's exhaust gases pass among the outer and the inner hub.
Into the interior of the Inner Hub the rubber hub enters which fits over the propeller shaft.
Diffuser Ring is the “raised rim” in which the Outer Hub of a “through-hub exhaust propeller” ends. Its role is to prevent exhaust gases from feeding back into propeller blades at low rpm, which would lead to the reduction of thrust.
The blades are the twisted fins which are attached to the propeller's hub.
Depending on the number of blades on the propellers we distinguish 3-blades, 4-blades or 5-blades.
Blade Face and Blade Back
The “blade face” is the side of the blade facing aft which pushes the water and moves the hull forward. The blade face is known as the high-pressure side or pitch side.
The “blade back” is the side of the blade facing the bow and the side that firstly meets the water. The blade back is known as the low-pressure side.
Blade Root and Blade Tip
The “blade root” is the part of the blade that attaches to the hub. The “nominal” pitch of a propeller is measured at this part of the blade.
The “blade tip” is the farthest point of the blade, measured from the center of propeller's hub. It is the point that separates the Leading from the Trailing Edge of the propeller's blade.
Leading and Trailing Edge of the blade
The “leading edge” is the forward edge of the blade which first cleaves the water when the propeller rotates. It starts from the front part of the propeller's hub and ends at the blade Tip.
The “trailing edge” is the aft edge of the blade from which the water leaves the blade or flows away. It starts from the blade Tip and ends at the rear portion of the propeller's hub.