The Kentucky Derby Festival’s Great Steamboat Race is undergoing some changes this year.Festival spokesman Mark Shallcross says three vessels will compete for the Golden Antlers on May 2-- the Belle of Louisville, the Belle of Cincinnati and the American Queen (pictured). "(The American Queen) is starting its maiden voyage upriver and will be stopping here for the boat race. It’s the largest steamboat ever built. It’s just huge, it looks more like a cruise ship. There are no tickets available for the American Queen, but there are a handful of tickets for the Belle of Louisville and there are still tickets left for the Belle of Cincinnati," he said.Shallcross says this year’s winner will be determined by points earned for completing a series of pre-race maneuvers in addition to the race itself.Meanwhile, a record number of runners will participate in this month’s mini-marathon and marathon.Shallcross says the number of entrants was capped at 18,000 this year, but could be expanded for future races if the infrastructure is in place."We’ll see how it goes this year. There’s a chance we could bump it up to 19,000 or 20,000. But we’re just kind of growing it incrementally," he said.There are still 200 spots available in this year’s races for runner who purchase a $125 “charity bib” during an April 26 runners’ expo at the Kentucky International Convention Center. Proceeds go to the festival’s charitable foundation.The marathons are Saturday, April 28.The Kentucky Derby Festival officially begins next Saturday with Thunder Over Louisville.