You don't have and don't need one.
As you know, the Yanmar 2QM15, does not have an engine kill switch. To shut down this engine you just retard the throttle until it dies. This works OK until you stall the engine while docking.I also lost my shifter cable one day, just as I was pulling into my slip and did not have reverse. The ball fitting broke away from the cable on the transmission end. It was only a small bump since we do not fly full speed into our marina and slip as do some of our more macho sailing buddies.