(T)his paper describes an investigation of variable valve timing applied to a turbocharged marine diesel engine. In order to maximise the specific output of a high speed turbocharged diesel engine, the valve overlap is usually greater than 90 degree Crank Angle (CA). The valve overlap allows the clearance volume to be scavenged around the non-firing top dead centre (TDC), assuming the turbocharging system is efficient enough to provide an excessive boost over the back pressure at that part of the cycle. The major disadvantage of overlap scavenging for high output diesel engines is almost inevitable reverse flow through the intake valve which occurs shortly after opening the valve at light load when the boost is insufficient to overcome the back pressure. This study considers how the intake valve timing affects the turbocharged marine diesel engine for reducing the reverse flow at the intake valve at light loads. The results of different valve overlap cases are plotted on the same diagrams and some cumulative figures are given in tables. Conclusions are drawn by utilising these diagrams and tables.