I would use a full strength white vinegar soak of at least 24 hours. Vinegar will cut the surface deposits but it may take multiple soaks to remove the deposits within the hose walls, if ever. I usually don't use muriatic acid as it's very strong, however, if the vinegar doesn't work you may have to try a diluted muriatic solution.

In the household cleaning sections of some superstores is a household cleaning product called "The Works" which is the diluted muriatic acid that webbee mentions above. I am not sure that will fix anything but it is an inexpensive product to try. I would add some dish-washing detergent too. Muriatic acid is used to adjust the pH of swimming pools. Perhaps you know someone who has some in the pool shed.