3D printing of spare parts on board ships is becoming an interesting idea due to advances in filament materials and printing technology. Several companies and navies have installed 3D printers on board a limited number of ships to test the feasibility. Further tests should be conducted to see if the printed spare part meets the stringent rules and standards for equipment on board ships. Thus, it also becomes a topic for future training of seafarers. In this paper, we present examples of the introduction of 3D printing into seafarers' training. An ideal example of a printed spare part is the universal key for an electric locker. It is often lost. Therefore, a spare part should be available. Fused Deposition Modeling (FDM) 3D printing technology is used by the students to obtain such a key. The printed key was tested on a real locker and served the purpose. In addition, students responded enthusiastically to the problem-based learning that is ideal for 3D manufacturing. The paper also introduces other printed parts.