The owner of the boat, called Bring It On, had only recently bought it. The vessel was gutted in the blaze, which was believed to have started in the engine bay, and later sank.
Fire, police and ambulance services were called to the Lake Rotoiti wharf on Otaramarae Rd about 10.30am yesterday after the alarm was raised by motorists on State Highway 33, near Okere Falls, and boaties on the lake.
The injured teenager was treated at Rotorua Hospital before being transferred to Waikato Hospital where he is listed as being in a comfortable condition.
The boat was about 300m off shore and heavily ablaze with the four occupants and two dogs in the water by the time help arrived. Firefighters with a portable pump used water from the lake to put out the blaze.
Taupo's Gary Newland was heading to the area with his boat when he saw the smoke across the lake. He called emergency services, launched his runabout and headed out to the burning boat.