I have a 48 MY with rocker switches for Ignition-Start-Stop. The lower helm ignition switch (on-on) is wired as a 3-way switch with the fly bridge helm. Has anyone added a key switch? Anyone can break in and start the engines.
Usually installed at the breaker panel. Find the breaker that controls that engine start/run and install a universal electric key switch there next or around it. Lost of older boats don't have a security switch for the mains. My 45 year old Bertram does not. When we are away from the boat for a while, I pull the Detroit shutdown flappers and trip the start breakers. We figure anybody who can break in, reset the flappers and re-set the breakers really wants the boat. It's insured, they ca have it and I'll give then a head start...