Abstract This paper describes a study on the application of a flame detecting system installed in a marine supercharged boiler. Flame images captured from experiments show that fluctuation of the flame in the supercharged boiler is intensive than that in stationary power plant boilers. Radiative Energy Signal (RES) is obtained from experiments by the flame detecting system, and it is shown that RES varies approximately linearly with the oil consumption rate and the heat absorption rate in the riser. Then, an instantaneous heat absorption rate is deduced from the real time RES by a linear equation, and a control strategy for the water level in drum by RES is proposed, in which the real time RES is used to control the flow rate of feed water in advance. Simulation results show that the fluctuating amplitude of the water level can be reduced significantly by introducing RES, and this control strategy has a great potential to improve the control quality of drum water level in the supercharged boiler.