That's the right control
It's a centerboard (read "light") rather than a swing keel (read "heavy"). The boat's lead ballast is encapsulated inside the shoal keel. That line at the bridge deck is attached to the centerboard. As you let the line out (feed it out, don't just let go) the centerboard will lower. Pulling the line in raises the centerboard. It doesn't get much simpler. A heavy swing keel which is the boat's ballast, like on a Catalina 22, usually is operated with a winch. Congratulations on your new acquisition - you've bought yourself a great boat!
