Once boiling, uncover and reduce the heat to medium. Cook until the potatoes are tender, about 8 to 10 minutes. Add the lobsters, 1-2 at a time, if needed, head first. Cook until the lobsters turn bright red, about 5 to 8 minutes. Remove the lobster from the pot. Add the sausage, clams, and corn. Cook until the clams open, about 5-8 minutes longer.