Predicting fuel consumption and performance of an outboard motor for a high speed small planing boat are numerically challenging. The propeller is one of the most popular propulsion systems used for outboard motors. We focused our attention on the fact that the thrust performance of a propeller has a major impact on cruising fuel consumption and performance. We believe that we can numerically predict cruising fuel consumption, which has conventionally been estimated through experiential means, using accurate thrust performance measurements via CFD simulation without cavitations model. This study aims to develop a simulator that could quantitatively predict cruising fuel consumption and performance of an outboard motor used for a high speed small planing boat. After comparing the CFD simulation of propellers against the results of model tests, the simulated results are in good agreement with the experimental results. In order to evaluate the accuracy of the fuel consumption and performance simulator, the simulation results are compared against the results of a full-scale cruising test. Comparisons between simulation and full-scale test suggest that the simulator can satisfactorily predict cruising fuel consumption and performance of outboard motors. In particular, prediction results agree with full-scale measurement results to within a range of ±1.42% (±0.81 km/h) for maximum speeds and ±4.89% for cruising fuel consumption. These results indicate that the simulator can quantitatively predict cruising fuel consumption as well as performance of an outboard motor. But more importantly, we understand that the simulator can be used to identify optimal propeller specifications and gear reduction ratio, which have traditionally been done based on experience. We, therefore, conclude that the simulator holds great potential as an effective tool that could be used to develop an environmentally friendly outboard motor with outstanding cruising fuel economy and performance.