We are in the process of re-tiling a corner jacuzzi tub, but we encountered a minor problem. After removing the old tile, there is a 3/4" gap between the tile and the tub, what do we use to fill this gap?

The tub has been spaced up to allow for the tile that was there at one time. The weight of the tub can't be supported by the outter lip of the tub instead it is supported by the base. Any how the top of the platform if there is a 3/4 gap. My fix would be to place 1/2 durock down on the top and then use 1/4 tile and that will fix that.

Glavine is correct, most of the whirlppols I have set do not put any load on the rim of the tiled surface. All the weight is carried directly to the floor below and then we build a shell around the tub with plywood and Hardiebacker or Wonderboard. Is your gap between the top surface of the tile and the underside of the tub rim?