The present invention relates to a novel apparatus and method for installing split line cutters on marine propeller shafts. The apparatus features a clamshell design comprising an upper and lower half, each with an inner cavity configured to accommodate a portion of the split line cutter. A hinge mechanism connects these halves, facilitating easy opening and closing around the propeller shaft. Key to this invention is a captive screw retaining mechanism within the clamshell, designed to hold screws in place even when unfastened, thereby simplifying the installation process and preventing loss of components. The apparatus includes a screwdriver opening aligned with a bolt cavity, allowing for engagement of captive screws. Additionally, the invention features temporary closure mechanisms, for secure handling during installation, and a retaining hole for attaching a line. This invention offers significant improvements in the installation of line cutters, emphasizing safety, efficiency, and ease of use.