Electronic Charting systems (ECS) in yachting and boating are the non-professional counterparts to ECDIS in commercial shipping. In the absence of legal regulations on design and use, a wide variety of products have de-veloped. Their usability is not only safety critical but often even determines whether navigation functions like route building or track recording are used at all. With two empirical studies employing standard usability meth-ods from human factors research, we assessed the usability of a variety of current ECSs on a sailing yacht. In study 1, nine usability experts conducted multimethod analyses while sailing in typical cruising areas on sea. Building on the results, a standardized user test was designed and carried out with 12 prototypical users plus 3 usability experts in inland waters (study 2). Finally, a set of 38 design and usability guidelines were formulated. The guidelines may not only help boat owners and charter companies in selecting a current market product but also aid manufacturers in designing their future products. Contributions: David Jung (study 1) and Martin Müller (study 2) conducted the studies and formulated the guide-lines. Gisela Müller-Plath designed and managed the research project ANeMoS (Analysing Use and Impact of NewMedia on Sailboats) which the present work is part of, commanded the sailing yacht, and wrote the paper.