A solar driven boat was constructed by the ESES, European Solar Engineering School, for the Frisian Solar challenge 2008 competition. All the parts of the electrical system were given by different sponsors. Of course the rules and specifications have to be kept. In my thesis some test is presented about system optimization and getting information about the missing data of the electrical components. The general aim of my work is improving the performance of the boat by testing the system parts and evaluating the results. In details –as sub-aims – we want to know the I-U curve of the panels, calculate the MPP losses of the panels and the charge controller losses. Finally the optimization of cable sizing is shown. For the I-U curve investigation a movable stand was built. In this way the panels had been hold and moved easily into or out from the radiation. Then the panels were connected to series connected adjustable loads while the values of the panel current and voltage were continuously measured. The experiment was done two times on different level of solar radiation (850W/m2 and 315 W/m2). Hereby we got the curve with all the important values. On the higher radiation level Isc= 8.3 A, Uoc= 34.9 V, MPP=210.2 W at Imp= 7.7 A and Ump= 27.3 V; on the lower one Isc= 2.9 A, Uoc= 34.5 V, MPP= 76 W at Imp= 2.5 A and Ump= 29.6 V. One of the basic ideas is reducing the losses. For this we have to measure the energy input and output of the controller; a data logger and a voltage divider are used for recording current and voltage values of the panels, load and battery. We can avoid the controller and the battery by bypass ways to get all mount of the energy to the motor from the panel. The mount of controller loss is between 0.67 W and 1.96 W, most of the time, but there is some huge peak in the graph. This can be possible because of the too high radiation and the too less load. This test was made with two PV panels in Borlänge, in the middle of March. Because of the short time and the late of the components test could not be repeated with higher load and higher radiation. Loss reduction is the reason why the motor is wanted to be connected directly to the panels. For this we have to know if the motor operates on the voltage and current level of the MPP of the panels. With other words the optimum operating point of the motor/panel combination should be explored. The experiment of the motor characteristic showed that in the view of energy generation keeping the minimal allowed speed is not a problem for the system. Getting 8 km/h average speed around 350 W is needed. If all the five panels are used in the same time around 300-315 W/m2 is enough for providing 350 watts. The last topic of the electrical circuit improvement is optimizing the cable sizes. For this not enough only to measure the distances between the components but we have to calculate some extra for the cable shoes and so on. Beside the correct length we have to find the perfect wire diameters, as well. Calculations are done by Microsoft Excel software, applying the standards of National Electric Code (NEC). During the tests the solar boat designed by the ESES team reached the 13km/h sailing speed. Power of the panels was presented in the first test. Around 1200 watts solar energy could be applied in case of 1000 W/m2 radiation. The mount of controller loss is between 0.67 W and 1.96 W, most of the time and for getting 8 km/h average speed around 350 W is needed.