The efficiency of the outboard motor is largely determined by the correct selection of the propeller. The efficiency, speed and throttle response of the entire system depend on it. How to choose the right propeller?
Instructions
Step 1
Use the easiest screw selection method. If possible, compare the performance of two or three screws with different pitch, alternately installing them on the same engine. Determine which propeller will be more effective when the boat is heavily loaded (usually a propeller with a smaller pitch), and which will provide high speed of movement with a minimum load of the boat or boat.
Step 2
Do some experiments by measuring fuel consumption for different boat loads. Determine for each propeller the optimum planing speed and the maximum speed the boat can reach. In this case, the motor should be running at approximately 5000 rpm at wide open throttle.
Step 3
When checking the operation of the screw, pay attention to how much water boils from under the motor. If, at the moment of the start of movement, the engine emits a sound that resembles a car over-gas, and responds abruptly and sharply to the movement of the control levers, it is required to install the propeller with a large step. With a poor set of revolutions and a slow exit to planing mode, a propeller with a smaller pitch will be required.
Step 4
When choosing a propeller for your boat, take into account the conditions of the planned operation of the boat, including the allowable load. If you plan to ride light, then the propeller designed for maximum load will make extra turns.
Step 5
Pay attention to the number of propeller blades. Three-blade propellers have a high maximum speed, but they bring the boat to planing more slowly. The four-bladed propellers, on the contrary, easily switch to the planing mode, but they are inferior to the three-bladed propellers in speed.
Step 6
The shape of the propeller blades is also important to ensure good travel. Choose elliptical blades if you want the best balance of speed and thrust. Some propellers have blades that taper towards the tips to reduce friction and are preferred for speed boats. For movement in water overgrown with algae, a propeller with blades twisted in the direction of rotation is more suitable.
Step 7
When choosing the material of the propeller, keep in mind that aluminum propellers are preferred for outboard motors mounted on small boats. They are lighter and cheaper than brass ones.
