Installing Boat Thrusters
Recreational and sports boats can either come already with thruster tunnels and propellers installed in their hull, or you may have to have a tunnel drilled in your vessel. It's best to let an experienced hand do the installation, as there is a complicated formula for determing the optimum placement of the tunnel, plus a compromise with other elements that might be present in the hull, like tanks and wiring, which will have to be compensated for by using another (usually more powerful) type of motor.
Custom installation is one of the services usually provided by suppliers of boat thrusters, usually done through their partnerships with local boat modifiers.
Depending on your boat's size and hull design, you can have single or double propellers, metal or composite materials, retractable or fixed axles, or one or two thrusters.
With a single bow thruster, you can counteract crossing winds or current, but with a stern thruster added, you can fully operate the boat sideways.
You can also have a time delay option for the motor. This ensures a delay of at least two seconds after the propeller stops before changing direction, which takes torque shock impacts out of the equation. Less shocks to the boat thruster's blades mean a longer-lasting boat thruster.
A major issue with installing thrusters is the possibility of increased drag on the hull when your boat is going forward. This is solved in two ways, depending on the type of boat you have. For sport boats that plane (lift) partly out of the water at cruing speeds, the tunnel for the thruster is placed in the part of the hull that lifts completely above the water. For boats with larger volumes, the water pressure is equalised inside and outside the operating thruster, which means less worries about drag. Still, you can install a scallop or fairing at the opening of the tunnel for optimum water flow.
Placing the tunnel is the most important factor in having an effective thruster. It must be fully submerged while running in order to prevent cavitation, which happens when the boat shudders from rotational forces in the hull and creates loud noises. It should also be placed as far forward as possible so the hull can act as a lever on the water. At the same time, thruster makers specify a minimum tunnel length for their devices to work. Finding a sufficiently thick point on the hull that addresses these issues without intruding on the rest of the boat's systems requires the service of a specialised installer.