The Coast Guard received a report of the boat being on fire in McCovey Cove, just south of AT&T Park, at approximately 4:10 p.m., Lutz said.
The 28 passengers were rescued by a Coast Guard 41-foot utility boat and transported to the South Beach Marina. No injuries were reported, he said.
San Francisco firefighters later determined the engine had overheated, fire officials said.
Firefighters towed the boat to South Beach Harbor, Lutz said.