This paper describes a method for early stage boat design by creating and utilizing a library of naval architecture based boat components in Modelica. The method involves the construction of stand-alone boat components which can be assembled into a simulation model. Structuring the model into multiple system levels provides a clear overview. Utilizing the partialcomplete methodology ensures that all system levels are replaceable within the simulation. This allows the user to construct many different boat models and experiment with unconventional or innovative designs. By comparing the performance and behaviour of different assemblies of components the most ideal design for a given purpose can be found and used as a starting point for the in-depth design process. By organizing the components in a library they can be re-used in future projects as well. It is noted that when additional libraries are utilized the effectiveness of this design method increases significantly. As the availability of component models increases, users can save time on the physical design and modelling of the individual components and instead focus on assembling working simulation models right from the beginning. To illustrate this, the construction of a few simple boat components is described in this paper. These components are then combined to simulate multiple concept designs.