ABSTRACT: The comfort on board is a fundamental parameter to deal with in the yacht design process. The acoustic comfort is a condition that has to be pursued in the yacht design process in order to meet the owner requirements and to allow the crew to work safely. The essential part of a ship propulsion system is the propulsion shaft line. The excitation forces originated from the shaft line can greatly affect the dynamic response of the whole ship structure. Yacht designers and builders are continuously looking for new solutions to reduce the noise and vibration on board a vessel. Within this context, the technical office of the Vulkan-Italia has developed a flexible coupling which, because of its modular and compact design, fits the installation requirements and guarantees excellent performance in terms of noise and vibration. In this paper, the operation principle of the elastic joint is explained and a numerical whirling vibration analysis is carried out. The whirling vibration analysis is able to check the shaft line with regards to vibrations due to the rotation of the shaft line and the hydrodynamic effects of the propeller.