Wash and peel the potatoes. Place in a large pot and cover with water. Boil, 30 to 45 minutes, or until tender. Drain and place in a large bowl.
Mash the potatoes until smooth. Stir in 1½ cups of sugar, flour, milk, extract, and butter; mix well. Taste and add more sugar, if needed. Stir in the eggs. Divide into the pie crust and smooth the top.
Bake 1 hour or until a knife inserted in the center comes out clean. Cool completely.