Modern ships are required to increase the energy efficiency and minimize fuel consumption. This paper presents the construction, main properties and exemplary measurement results of a novel system intended for main shaft power monitoring. The telemetry system consists of the stationary part, responsible for wireless supply energy transfer to the rotating part. Additional functions of the stationery unit include radio-based, bidirectional communication with the rotating, microcontroller-based unit, and Modbus-based communication with the graphical user interface. The non-stationary (rotating) part receives the necessary energy using the wireless transmission and performs the torque and speed measurement using strain gauge and a special setup of the wireless energy system. A novel system of flexible printed circuit board (PCB) coils is used for wireless energy transmission and increases the flexibility of the device while minimizing the necessary size, weight, and costs of the setup. The microcontroller unit used for measurements allows proper sampling of highly dynamic signals and can be used for advanced drive system diagnostics or as a typical power monitoring device. Such unit was installed on a ferry and operation was monitored for several sea trips. Main results depict characteristic power data referenced to vessel speed and specific fuel oil consumption (SFOC). Proposed system construction allows to reduce system costs and provides stable readings for long period of operation.