A bow thruster adds easy control of the bow at slow speeds to counter the effects of wind, current and prop walk. The desired lateral movement becomes a reality with a thruster. This is enables the person at the helm to maneuver a boat easily into tight dock spaces or moorings. Thrusters operate by an electrically or hydraulically driven propeller that pushes thrust laterally, enabling the bow of a boat to move sideways. Controls from the helm station allow the pilot to move the bow of the vessel to either port or starboard. In a similar manner, the stern of the boat can also be controlled, by installation of a stern thruster. Bow and stern thruster combination add balanced sideways thrust, enabling a boat to slide sideways without moving ahead.
Vetus offers thrusters in both electric and hydraulic versions, Lewmar in electric version. Thrusters with electric motors are easiest to retrofit into a boat, and work excellent. The only drawback to electric motored bow thrusters is the duration for which a thruster can be operated. Due to heat build up in the motor, electric thrusters are only operable for a few minutes every hour. Under normal operating conditions, this poses no problem. Also, if an electric motor is placed in a void where there exist risks of fuel fumes, it will need to be ignition protected. Electric thruster installation should incorporate a dedicated battery bank. For most applications, AGM style batteries are preferred because it eliminates gas emissions and acid leakage typical of lead acid batteries.
Hydraulic thrusters are the optimum choice for boats which use hydraulic systems. Hydraulic thrusters are very powerful and hydraulic motors have no operating time limitations. The cost of the hydraulic version is more expensive, but one hydraulic motor can operate the thrusters, windlasses, winches, hatches and davits, thus reducing weight, expense and offering more power than electric versions. In most cases cost and installation of a hydraulic thrusters is beneficial on boats that incorporate hydraulics.