Advance HCD1600 Marine Gearbox The Advance 1600 series marine gearbox has the functions of reverse, forward, clutch, deceleration, and withstand propeller thrust. The HC1600/HCD1600 gearbox has a vertical off-center primary transmission structure, and the HCT1600/HCT1600/1 gearbox has a vertical off-center secondary transmission structure. This series of gearboxes have the characteristics …