There have been a lot of questions like this here and on other boards I visit. I agree, the short answer is 'Too much oomph' in the cast. Relax a little and let the rod sling the line out.
It just struck me the other day - near the beginning of the movie RRThoughIt, the father is teaching the boys to write. They hand in their work and he replies, "Good, now half as many words". So it is with casting, "Good, now with half the energy" ... just make a firm stop.