The extent of the injuries were not immediately released, the injured included children.
Park Superintendent Cheryl Vincent says all the injured were on the boat, which was on a trailer being loaded into the water when the explosion and fire happened just before 1:00 p.m.
An off-duty firefighter witnessed the explosion and called for help.
Lake Hamilton Fire crews, Arkansas Game and Fish officers, Arkansas State Police, Diamond Head police, and Hot Spring County sheriff’s deputies assisted Lake Catherine park rangers in responding to the emergency.
Three of the injured were flown by air ambulance from the scene.
The cause of the explosion is being investigated by the Lake Hamilton Fire Marshal.