Your goal is reasonable for your height to weight ratio. Also the time frame in which you want to accomplish this.
I don't think fasting with water only is meant for weight loss. Weight loss really happens when you eat right and exercise. So first think about what made you gain all this weight. Also if you don't stop and change the way you eat, you will gain it all back.
My suggestion is do Master-Cleanse
first for 10 days, then go in to water only fast (nothing but water in your mouth, no toothpaste, supplements, chewing gum, etc) till you acieve your goal, but how you break your fast and what you eat will matter. If you are going to go back to eating what you eat you will gain back the weight very easily.
Another thing to do while fasting and not fasting as well is to walk 20 minutes everyday.
There is one more way, that is to be on juices that are squeezed fresh from organic fruits and vegetables. Make sure not to combine fruits and veggies, drink them separately.