Effective Reduction of Noise and Vibration of Internal Combustion Engines in Marine Installations

The use of larger and more powerful engines in marine pleasure craft coupled with lightweight boat construction is causing excessive noise and vibration which boat owners find objectionable. This is especially true in the case of Diesel engines which are increasingly used in pleasure craft due to the lower risk of explosion associated with diesel fuel, and lower fuel consumption.

The mountings presently used in marine installations are typically bushings which have a uniformly high stiffness rate and do not attempt to isolate low engine speeds. The lightweight construction now employed by boat builders no longer permits this approach.

Instead, mountings must be designed with the proper stiffness rates in each axis (vertical, longitudinal, lateral) to independently handle propulsion loads and still provide isolation of engine generated dynamic disturbances to a level that is acceptable to the boat occupants. The isolator design must also limit engine motions to prevent propeller shaft problems.