A system for removably mounting a trenching attachment to hook and eye mounts on an end of a power unit. The trenching attachment includes a mounting frame having hook-engaging shafts and eye-engaging pins, a head drive assembly, a trenching boom assembly pivotally mounted to the head drive assembly, and a hydraulic boom cylinder for raising and lowering the boom assembly with respect to the mounting frame. With the boom assembly supported in a three-point stance adjacent the power unit, the cylinder is actuated in a first direction to rotate the mounting frame with respect to the boom assembly, and engage the shafts with the mounting frame hooks. Further actuation of the cylinder in the first direction rotates the mounting frame with respect to the boom assembly and power unit until the mounting frame pins are adjacent the mount eyes. A grease cylinder on the mounting frame is actuated to extend the pins and engage the mount eyes. The trenching boom assembly can then be raised off the ground by actuating the cylinder in a second direction. Four sets of hook and eye mounts are located at equally spaced and laterally separated positions on the end of the power unit permitting the trenching attachment to be mounted at either centerline, partial offset or full offset trenching positions. When in the full offset position the trenching boom assembly is aligned with a side of the power unit. An auger and auger shaft located on the same side of the power unit as the boom assembly can be removed to permit trenching adjacent a structure.