For the third time this year the Coast Guard has shut down boats violating passenger and charter rules. The 50-foot yacht “Shady Shack” was stopped in the Gravois arm on Friday for carrying 24 passengers. On Saturday, the Coast Guard stopped a 42-foot boat, the “Play Pen” for carrying 15 passengers. Neither boat had a valid certificate of inspection or a certified mariner, among other violations. Owners and operators of the boats face maximum penalties including fines of over $41,000 for illegal passenger-for-hire operations.