The fire was reported just before 3 p.m. aboard the 44-foot vessel Laetitia, which was about nine miles off King Harbor, according to the Los Angeles Fire Department and U.S. Coast Guard.
A mayday call was issued on an emergency radio channel reporting an engine fire was spreading, according to the Coast Guard's Sondra Kay Kneen.
The three passengers aboard were advised to don life jackets and move to the bow of the boat to avoid the fire, she said.
One of the boaters jumped into the water and was quickly rescued by county fire department lifeguards and Coast Guard personnel rescued two others from the stricken craft, Kneen said.
The Laetitia was fully involved in flames when firefighter/lifeguards arrived, authorities said.
One of the mariners sustained burned hands and the other two were unharmed, Kneen said.