Abstract: A one-piece marine gear casing includes a cross-shaped slot therein as seen in a plan view. The cross-shaped slot permits lowering a bull gear with its attached shafts into the gear casing. The slot is transversely braced after installation of the bull gear to reduce the possibility of vibration of the housing. The cross-shaped slot is enlarged at its lower extremity to permit the installation of upper bearing halves in opposition to lower bearing halves in the gear casing. The upper and lower bearing halves provide rotatable support for the shafts of the bull gear. Upper surfaces of the gear casing provide support for additional lower bearing halves for the shafts of gears and pinions employed to transmit torque from one or more input shafts to the bull gear.