Abstract: A ship propulsion unit includes a propeller pod (14) provided with a propulsion propeller (15) and a turnable shaft (2) attached to the propulsion pod. The turnable shaft is journalled in the hull (1) of the ship by a rotation bearing (4) mounted in the hull and a rotation mechanism (3) mounted in the hull is coupled to the turnable shaft for turning the shaft. A seal (5) is provided in an annular space (9) between the turnable shaft and the hull for protecting the rotation bearing and the rotation mechanism. The propulsion unit is releasably attached to the hull by an attachment mechanism (6) which holds the propulsion unit in an operative position relative to the hull. A support arrangement (7, 8; 11, 12, 13) supports the propulsion unit at a position below its operative position when the attachment mechanism is released.