This paper is the result of a final degree project, consisting in the design of a propulsion system for a transportation boat based on electric motors powered partially by solar energy comparing its costs with a conventional propulsion system by combustion engines. The boat is meant to be used to transport up to 30 passengers and 1 ton of goods on the Paraguay River in the northern part of the Paraguayan Chaco region. First was designed the most suitable hull, for which simulations were executed with computerized software with the main aim to optimize the hydrodynamic resistance of the vessel obtaining as outcome a 10 m long and 4.7m wide catamaran. Then was carried out the complete sizing of the electric propulsion system, including the photovoltaic array integrated into the roof of the boat, charge controllers, battery banks, electric motors, recharging stations and BOS. The dimensioning was made considering a route between various places located on an almost 250 km long section of the Paraguay River. The economic study showed that applying the Present Value of Costs for the solar propulsion system is 3 times lower than the one for the conventional system for a 10 years’ period.