A sprinkler includes a turbine, a nozzle, a gear train reduction and a reversing mechanism that rotatably couples the gear train reduction and the nozzle. The gear train reduction includes an input stage and a planetary gear drive output stage that includes a first portion of the reversing mechanism. A second portion of the reversing mechanism is located outside of the gear train reduction. The second portion of the reversing mechanism includes a pair of arc tabs. At least one of the arc tabs is adjustable to establish an arc of coverage of the sprinkler when the water flowing past the turbine causes the gear train reduction and the reversing mechanism to oscillate the nozzle back and forth between a pair of arc stops. The arc stops are defined by the locations of the arc tabs. The input stage of the gear train reduction includes a mechanism that allows manual rotation of the nozzle between the arc stops without having to back drive the gears in the input stage.
