Cover yams with water; add salt and cook until tender.
Peel yams and mash until smooth.
Add remaining ingredients, except 1/2 cup coconut and marshmallows.
Place in a greased 2quart casserole.
Bake at 350 degrees for 30 minutes.
Sprinkle with enough marshmallows to cover; top with coconut.
Brown lightly before serving.