Spice section, cheap, nontoxic, not pleasant for animal snoots and mouths. Refresh it once in a while.
I've used it to keep tomcats from lurking around bldgs and vehicles. You definitely don't want to encourage cats to hang around your boats; the piss stench never comes out even with multiple washings with various cleaners.
Look up "natural animal repellants" or similar phrase. You can use mothballs, too, but be careful how you do it. I've hung them in cheap nylon hose that I cut into tube sections and tied off at both ends, then hung up a few inches above the ground but under dry cover. That way, they can't contaminate the soil from rain soakings.