Place gelatin in a large metal bowl. Add boiling water and stir until dissolved. Drain pineapple in a strainer over a 2-4 cup liquid measuring cup. Set pineapple aside. Add to gelatin.
Half fill a large bowl with ice cubes and cold water.
Set bowl with gelatin in ice bath and stir occasionally with a rubber spatula until mixture is thickened. Remove bowl of gelatin and fold in remaining ingredients. Pour into the mold. Refrigerate for at least 4 hours or until very firm. Check on mold after about a half hour-if marshmallows are concentrated on top, gently push them down and stir in with rubber spatula.