Numerical simulations were used to optimize the casting design and conditions for large cast iron castings for marine engines. Simulations of the mold filling and solidification sequences were used to ana- lyze the problems of previous casting conditions with marked improvements for large cylinder liner parts. The amount and positions of chills were optimized to improve the mechanical properties and to minimize the shrinkage and micro porosity in the castings. Ultra sonic testing, penetration testing, and mechanical prop- erty testing show no defects in the castings with the productivity significantly increased.