A monohull offshore drilling vessel includes a hull with a moonpool and a multiple firing line hoist system mounted on the hull. The multiple firing line hoist system includes a mast having a top side and a base connected to the hull, wherein the mast has a hollow construction with a first side and an opposed second side. A first hoisting device is supported by the mast and has load attachment device displaceable along a first firing line, which extends on the outside of and adjacent to the first side of the mast. A second hoisting device is supported by the mast and has a load attachment device displaceable along a second firing line. The first and second hoisting devices each include one or more cables and one or more associated winches to manipulate the position of each of the load attachment devices relative to the mast.