1/2 cup sugar
1 1/2 cups lemon juice
3 cups light rum
1/2 gal unsweetened pineapple juice
1 1/2 giggers of grenadine

Mix items together in a large covered plastic container; freeze.

To serve, scrape with a large spoon.

Fill the glass and add a bit of Fresca (optional). You can also use 7UP or Sprite instead.