Marine diesel engine excitation can occur from the cycle-to-cycle variation in the engines output. The cycle-to-cycle variation in maximum cylinder pressure (P,,=,) is often used to represent this variation. Earlier studies examined the correlation between the cycle-to-cycle variation in the maximum cylinder pressure (Pm~), pressure impulse (PI), and ignition delay (ID), for the case of constant injection setting. Recent studies showed the injection timing strongly affects the cycle-to-cycle variation. This paper summarizes the results of systematic experiments to determine cycle-to-cycle variation for a single-cylinder diesel test engine and extrapolation to estimate the cycle-to-cycle variation in a 12-cylinder 925-hp diesel propulsion engine. Comparison of the extrapolated and measured results shows reasonable agreement.