Broward Sheriff Fire Rescue units responded to the Harbour Towne Marina, at around 11:30 a.m., Saturday.
Crews arrived to find the victims suffering from second-degree burns on their upper and lower extremities.
Investigators said fuel was coming from the boat, and there were vapors in the engine when the women were preparing to go out on the vessel.
When they started the engine, officials said, there was a vapor explosion that caused a small fireball.Crews were able to put out the flames.
Paramedics transported the women to Broward Health Medical Center in serious condition. They are all expected to be OK.