Cook sweet potato in boiling water to cover 15 minutes or until tender; drain. Combine sweet potato and 3 tablespoons margarine in a large bowl; mash. Add orange juice and next 5 ingredients; stir well. Spoon mixture into 4 lightly greased 8-ounce ramekins; set aside.
Combine 1/4 cup brown sugar, flour, 1 1/2 tablespoons margarine, and chopped pecans; sprinkle evenly over sweet potato mixture in ramekins. Bake, uncovered, at 350° for 20 minutes or until bubbly.