An irrigation sprinkler can include a riser and a nozzle turret rotatably mounted at an upper end of the riser. A drive assembly supported in the riser can be coupled to the nozzle turret for rotating the nozzle turret. The drive assembly can have a reversing gear drive, a reversing mechanism, and a manually adjustable arc setting mechanism including a pair of arc tabs. A position of one of the arc tabs is adjustable through the arc setting mechanism to change a size of an angle through which the nozzle turret oscillates back and forth. The manually adjustable arc setting mechanism is further adjustable to allow the nozzle turret to continuously rotate.