The paper provides brief historical information related to the development of ship electric drives. The issues of theory and operation of the main ship electric drives are described. Particular attention is paid to the phenomena to which the actuators of the mechanisms are exposed, creating by means of transmission devices or directly loads on the shafts of the engines of ship electric drives. Main methods of calculation and selection of power (drive and actuating) electric motors of main drives of commercial and fish fleet vessels are considered.