Kathy, I thank you for posting your recipe. I found it on Thanksgiving day and baked it. My mother had PLENTY of sweets in her kitchen, but after I made your sweet potato cake, no one even TOUCHED any other sweets until mine was gone (the next day)! I hope you don't mind that I had to revise it a little, so for a 13x9" pan, try the following:

Cake:
1 (18.25-ounce) package yellow cake mix (Deluxe Moist)
1 (15 1/4-ounce) can crushed pineapple, DRAINED WELL.
1 (15-ounce) can sweet potato pieces, drained & mashed
1 cup water
3 large eggs
2 tablespoons SMART BALANCE spread softened but not melted.
1 teaspoon ground cinnamon
1/2 teaspoon ground nutmeg
1 teaspoon vanilla extract

Preheat oven to 350F . Grease and flour one 13x9" cake pan; set aside.

Place all ingredients for cake in a large mixing bowl and beat at low speed with an electric mixer for 3 minutes. Distribute the batter evenly in the cake pan.

Bake for ONE HOUR or when pressed lightly in the center and cake springs back. Cool in pan on wire racks 10 minutes and if you want, chill in fridge for 20 min to speed cooling process. Leave in pan. (I used the cheap aluminum pans that come with plastic cover; you use a couple of times, then throw away).

Frost cake as desired with Cream Cheese Frosting
Makes 1 DELICIOUS (13x9) cake.

WARNING: This cake is addictive. Be sure to excersize before, during & after cake is gone ;-)