1. 3 or 4 blades?
A 3-blade propeller usually offers top speed performance while a 4-blade propeller provides maximum thrust and smooth cruising operation.
Diameter is the distance across a circle encompassing all of the propeller blades.
Pitch is the theoretical distance that a propeller will move though the water for each revolution assuming that there is no slippage.
4. Right hand or left hand rotation?
In most cases, right hand propellers are used for single engine applications and one left hand propellers are used for twin engine applications to achieve better steering control.
5. Cupped blades:
This is a technique used to enhance the performance of propellers under certain conditions. A cupped propeller will exhibit very high efficiency at high speeds as well as minimize cavitation under heavy loads.
Rake is a special design feature. Positive rake benefits from normal bow lift to permit the use of a larger diameter propeller, while negative rake can provide extra blade strength for use in very high speed applications.
7. Type of material aluminum or stainless steel
The most common materials of construction of propellers are aluminum and stainless steel. The aluminum propellers are the most widely used in cruisers. They are economical, while they are performing well. They do not corrode easily while they are repaired cheaply and easily. In contrast, the stainless steel propellers are five times stronger than aluminum ones. They are much more resistant to corrosion and do not project losses. Usually placed in vessels with high horsepower engines.
1. Type of boat (Cruiser, ski, runabout, bass, pontoon)
2. Prop on boat now (Brand, model, diameter, pitch, cupping)
3. Engine RPM at wide open throttle (WOT)
4. Speed of boat over water at WOT
5. Normal operating altitude (Motors lose 3% of power per 1000ft.)