The physical placement of the thruster on the hull impacts the thrust available. A position further against the bow will significantly increase the sufficient thrust due to the weight arm principle, as the thruster is further away from the boat's rotation point. 

The example below shows the different wind speeds that two different thruster installations can counter and the increased leverage gained when the thruster position is further forward.

Electric tunnel thruster with 130 kg of thrust
Position A: 21.2 knots 
Position B: 22.4 knots 

Electric tunnel thruster with 170 kg of thrust
Position A: 23.9 knots 
Position B: 25.2 knots 

If you cannot fit a thruster in a good position, it is advised to consider a retractable or external thruster. 

The windage area above the boat's waterline is a key factor when calculating a thruster model's theoretical performance. These calculations aim to predict what wind force a given thruster is able to push the boat's bow or stern against.

An installer needs an accurate assessment of your boat's total windage area in square meters of the hull's topside profile above sea level. If there are strong currents in the harbors you frequently find yourself in, you should also take this into consideration. 

When it comes to finding the thruster right for larger vessels, the expression comes true - bigger is better. Why?

Ensuring you satisfy the guidelines outlined in our tunnel guide (found here) and the tunnel can be correctly installed adequately under the waterline, having a larger tunnel comes with many advantages. While our smaller range thrusters come with a powerful electric or hydraulic motor, they generate tremendous amounts of water flow through a small tunnel diameter. While potentially producing enough force to manouver a larger vessel, the immense water flow through a smaller tunnel will be creating some cavitation* in the tube, resulting in increased noise and strain during operation.

Alternatively, larger tunnels and thrusters require fewer propeller revolutions to produce the same force reducing cavitation and strain on the motor, resulting in a smoother, quieter operation when you need it the most.

*Cavitation is a phenomenon in which the static pressure of the liquid reduces to below the liquid's vapor pressure, leading to the formation of small vapor-filled cavities in the liquid.

Voltage drop caused by inevitable resistance from other components affects thrust power. To obtain a thruster's rated performance, you need to calculate with loss of voltage through the battery cables, main switch, and fuse. 

Typically, in a 12V system, you will find that you only get 10-11 volts reaching the electric motor. This is a significant energy reduction that directly affects the thruster's output. If you have decided you need 130 kilos of force for your vessel but only get 110, you will probably be disappointed. 

A word of caution is that some manufacturers state the rated thrust at unrealistic voltage levels, making it more challenging to compare different brands. Make sure to acquire realistic thrust performance before deciding on a specific model. 10,5 volts is a typical value in a proper installation. 

Another option is installing a dedicated battery close to the thruster to reduce high voltage drops from very long battery cables. Remember that the battery needs an enclosed and ventilated battery enclosure if installed in a cabin.