To reduce the vibration and noise level in ships, marine propulsion engines are conventionally supported by rubber mounts. But the design of a rubber mounting system for medium- and low-speed propulsion engines could be very complicated due to the large stiffness and rubber creep of rubber mounts. Air spring, which is superior in many respects to rubber mount, can be used as the propulsion engine mounting system. The superiority and potential of pneumatic mounting system is discussed in this paper. The pneumatic system’s loading and stiffness characteristics, which are distinct from rubber system, are analyzed. And an optimized air pressure distribution among air springs is given. The system natural frequencies and force transmissibility are calculated based on a fictitious propulsion engine model. The results show that the pneumatic mounting system can effectively attenuate the dynamic force transmitted to the ship floor, and the system characteristics are not apparently affected by the air pressure distribution.Copyright © 2007 by ASME