A sealing unit longitudinally comprises first and second sealing sub-units disposed around first and second portions of a driveshaft of a marine propulsion system of a watercraft. The first sealing sub-unit is sealingly connected to a front wall of the hull and the engine casing. The second sealing sub-unit is sealingly connected to the driveshaft and a crankshaft. The second sealing sub-unit is disposed at least partially inside the first sealing sub-unit. An inside of the first sealing sub-unit is in fluid communication with a water intake ramp. An inside of the second sealing sub-unit is in fluid communication with an interior of an engine. The first sealing sub-unit prevents fluid communication between the water intake ramp and a portion of an inside of the hull. The second sealing sub-unit prevents fluid communication between the engine, the inside of the hull, and the water intake ramp.