A device for reducing the drive power requirement of a ship and even for not very quick ships of all types, in particular for slow, wide ships, such as tankers, bulkers and tugboats, and for improving the propeller blower stream as well as for producing a pretwist includes a front nozzle fixedly installed on the hull with fins or hydrofoils placed in the inner space thereof. A system includes a power supply input configured to receive power from a time-varying input voltage source. The tube being tested prior to and during sealing. The slide bar has on its upper end a magnet, thus vertically moving the actuating rod by magnetic force.