Combine sweet potatoes,carrots,1/2 cup coconut,sugar,butter and salt in crockpot. Cover;cook on low 5 to 6 hours or until sweet potatoes are tender.

Heat small skillet over medium heat,add remaining 1/4 cup coconut;cook and stir 4 minutes or until lightly browned. Transfer to small bowl;cool completely.

Mash sweet potatoes. Stir in 3 tablespoons walnuts and lime peel. Sprinkle with remaining walnuts and toasted coconut.