No, a tower is not necessary for w2w jumps, although it will help. I ride behind a number of boats, 1 with a tower, 1 with a pylon, and several right off the back of the boat. It sounds like you ride behind an outboard boat, what kind is it? Another issue may be wake size. Most outboard boats don't tend to put off very good wakes. I/Os when weighted and trimmed properly can put out decent wakes, but inboards still put out the best. IMO, the 3 ingredients in order for good pop and distance are 1) technique (speed+position+pop) 2) wake (size+shape+firmness+height), and 3) tower or pylon.
I get my most effortless w2w jumps behind a weighted inboard with a tower, but I have landed way out in the flats behind just a loaded I/O with no tower. Keep working on your technique and when you get a chance to ride between a real wakeboard boat, you will be way ahead of the game.