Auxiliary engines (generator sets) are as important as main engines in ships. They are accepted as the primary sources of vibration on vessels. In this study, we have designed new foundations for a specific type of generator set such that they may be used as vibration reducers. We have designed these foundations for different geometrical parameters to obtain the optimal shape for vibration reduction. We implemented harmonic vibration analyses via the finite element method on a realistic global ship hull model for these foundations and compared the results to the foundationless state. Finally, we determined the most effective foundation designs for different situations. The results clearly show that our design approach is very effective for vibration reduction of marine gensets.