A propulsion drive assembly for a marine vessel, said propulsion drive assembly comprising: a propeller drive unit for carrying and driving at least one propeller, a housing for connection to a hull of the marine vessel on an inside of the hull such that the housing surrounds a first opening of the hull and seals to the hull, wherein the housing defines an inner space and wherein the housing is provided with a second opening through which the at least a portion of the propeller drive unit is movable into and out of the inner space through the first opening, a suspension mechanism attached to the housing and configured to suspend the propeller drive unit, wherein the suspension mechanism is movable along a first longitudinal axis of the housing between a stowed position, in which the propeller drive unit is positioned inside the inner space of the housing, and a deployed position in which at least a portion of the propeller drive unit protrudes outside the housing through the first opening, and a gas supply device configured to supply gas into the inner space of the housing, said gas supply device comprising a gas pump or a controllable valve connectable to a source of pressurized gas, wherein the suspension mechanism comprises a piston guided within the housing for movement along the first longitudinal axis, wherein the propeller drive unit is attached to the piston, wherein the piston seals to the housing thereby separating the inner space into a first space adjacent the second opening, and a second space on the opposite side of the piston, and wherein the gas supply device is configured to provide said gas supply into the first space, wherein the suspension mechanism comprises an actuator assembly configured to control movement of the suspension mechanism between the stowed position and the deployed position, wherein the housing comprises a first end portion for connection to the hull and an opposite second end portion, wherein the actuator assembly comprises an actuator and a drive mechanism controlled by the actuator, characterised in that said drive mechanism being attached to the second end portion of the housing and to the piston. a propeller drive unit for carrying and driving at least one propeller, a housing for connection to a hull of the marine vessel on an inside of the hull such that the housing surrounds a first opening of the hull and seals to the hull, wherein the housing defines an inner space and wherein the housing is provided with a second opening through which the at least a portion of the propeller drive unit is movable into and out of the inner space through the first opening, a suspension mechanism attached to the housing and configured to suspend the propeller drive unit, wherein the suspension mechanism is movable along a first longitudinal axis of the housing between a stowed position, in which the propeller drive unit is positioned inside the inner space of the housing, and a deployed position in which at least a portion of the propeller drive unit protrudes outside the housing through the first opening, and a gas supply device configured to supply gas into the inner space of the housing, said gas supply device comprising a gas pump or a controllable valve connectable to a source of pressurized gas, wherein the suspension mechanism comprises a piston guided within the housing for movement along the first longitudinal axis, wherein the propeller drive unit is attached to the piston, wherein the piston seals to the housing thereby separating the inner space into a first space adjacent the second opening, and a second space on the opposite side of the piston, and wherein the gas supply device is configured to provide said gas supply into the first space, wherein the suspension mechanism comprises an actuator assembly configured to control movement of the suspension mechanism between the stowed position and the deployed position, wherein the housing comprises a first end portion for connection to the hull and an opposite second end portion, wherein the actuator assembly comprises an actuator and a drive mechanism controlled by the actuator, characterised in that said drive mechanism being attached to the second end portion of the housing and to the piston.