A hydraulic control apparatus for marine reversing gear assembly for watercraft includes a pressure-reducing valve for adjusting pressure of working oil supplied from a supply pump, and supplying working oil to forward and reverse clutches; a proportional electromagnetic valve for controlling the supply of working oil to a pilot chamber of the pressure reducing valve; and a spring-type switching valve for switching to a circuit for supplying working oil to a control piston chamber for controlling a spring force of the pressure-reducing valve or to a circuit for draining working oil from the chamber; wherein a pressure output from the proportional electromagnetic valve acts upon the switching valve as a pilot pressure; and, when the pilot pressure falls below a predetermined value, the switching valve switches to the circuit for supplying the working oil to the chamber via the spring of the switching valve, fully opening the pressure-reducing valve.