In this paper, it is pointed out that the battery contained in the plug-in hybrid boat, PHEB, has a high potential for the real electrification of a small boat for providing outstanding performances. The purpose of this paper is to encourage the spread of such a useful PHEB system for small cruising, fishing and working boats. The PHEB system is equipped an internal combustion engine, electric motor, battery, and an electric charger for shore power receiving system. For the practical use of PHEB, it is also suggested to equip electric generators. According to experience, the PHEB works very well with silence, low pollution, and low CO2 emission during the electric mode together with the ICE’s usefulness represented by the robustness of the fuel infrastructure and high energy density. Three PHEB’s were produced and introduced to show the usefulness for boating.