A marine propulsion system comprising: an input shaft that is connectable to a source of motive power; a transverse shaft that has a transverse orientation relative to the input shaft and that is connected to receive motive power from the input shaft; a pivot gear set of bevel gears for transferring motive power from the input shaft to the transverse shaft; a drive shaft (26,30) that extends perpendicular to the transverse shaft; a clutch assembly configured to transfer motive power selectively from the transverse shaft to the drive shaft (26,30); a propeller shaft connected to receive motive power from the drive shaft (26,30); a gearbox housing supporting the input shaft and transverse shaft for rotation about their respective axes; a pivot casing supporting the drive shaft (26,30) for rotation about its axis, said pivot casing being configured to pivot relative to the gearbox housing, about the axis of the transverse shaft; and a lower unit housing supporting the propeller shaft for rotation about the axis of propeller shaft, said lower unit housing being configured to pivot relative to the pivot casing, about the drive axis of the drive shaft (26,30); wherein the clutch assembly includes: a pair of bevel gears, comprising a forward gear and a reverse gear, each supported for rotation about the transverse shaft; a clutch element, configured to connect the forward gear or the reverse gear to the transverse shaft, to receive motive power from the transverse shaft; and a bevel gear disposed on the drive shaft (26,30) and meshed on opposing sides with the forward gear and the reverse gear characterised in that said marine propulsion system includes an intermediate shaft, extending generally parallel to the input shaft and connected to receive motive power from the input shaft via a gear set, said intermediate shaft being connected to the transverse shaft via the pivot gear set; wherein the intermediate shaft axis extends at a higher elevation than the input shaft axis. an input shaft that is connectable to a source of motive power; a transverse shaft that has a transverse orientation relative to the input shaft and that is connected to receive motive power from the input shaft; a pivot gear set of bevel gears for transferring motive power from the input shaft to the transverse shaft; a drive shaft (26,30) that extends perpendicular to the transverse shaft; a clutch assembly configured to transfer motive power selectively from the transverse shaft to the drive shaft (26,30); a propeller shaft connected to receive motive power from the drive shaft (26,30); a gearbox housing supporting the input shaft and transverse shaft for rotation about their respective axes; a pivot casing supporting the drive shaft (26,30) for rotation about its axis, said pivot casing being configured to pivot relative to the gearbox housing, about the axis of the transverse shaft; and a lower unit housing supporting the propeller shaft for rotation about the axis of propeller shaft, said lower unit housing being configured to pivot relative to the pivot casing, about the drive axis of the drive shaft (26,30); wherein the clutch assembly includes: a pair of bevel gears, comprising a forward gear and a reverse gear, each supported for rotation about the transverse shaft; a clutch element, configured to connect the forward gear or the reverse gear to the transverse shaft, to receive motive power from the transverse shaft; and a bevel gear disposed on the drive shaft (26,30) and meshed on opposing sides with the forward gear and the reverse gear a pair of bevel gears, comprising a forward gear and a reverse gear, each supported for rotation about the transverse shaft; a clutch element, configured to connect the forward gear or the reverse gear to the transverse shaft, to receive motive power from the transverse shaft; and a bevel gear disposed on the drive shaft (26,30) and meshed on opposing sides with the forward gear and the reverse gear characterised in that said marine propulsion system includes an intermediate shaft, extending generally parallel to the input shaft and connected to receive motive power from the input shaft via a gear set, said intermediate shaft being connected to the transverse shaft via the pivot gear set; wherein the intermediate shaft axis extends at a higher elevation than the input shaft axis.