Cars are really not designed to be tow vehicles although there will probably be some that will answer " I towed my 21' Bass boat with my Civic" I think you have to add the weight of the people in your vehicle plus don`t forget fuel for the boat and your gear.
I believe most cars have a tow rating of 1000 lbs and know matter how you slice it you will be over.
Personally I would never tow a boat that weighed more than a few hundred pounds with a car,you have to think about safety is your family going to be in the car with you?.
There may be warranty issues and possibly insurance and highway traffic act issues aswell.
Sometimes if you wanna play ya gotta pay!