Doesn't take a whole lot of skill to stick a hot poker in someone's eye, tear off fingernails, chop off fingers or toes, or flog someone.  Trapped on a ship, it's not like they'll have access to a rack or some of the other more elaborate ways of torture.  But yes, if someone had knowledge of where that last piece of the map was, it might be wiser to go with a professional, though keeping one under constant employ doesn't seem to be economically sound.