In addition to the great advice from loophitech and loco_alto...
I use heavy flies, often weighted, when fishing for saltwater species and find these things to be helpful:
- try shorter compact tapers, like the Rio Clouser line
- use a more gradual speed-up to the stop with a longer path of the rod tip if not already
- switch to a shorter / stouter leader
- cast with more line out of the guides (i.e. the whole head)
- tie the buggers with a little more tail material to add a little drag to reduce the jerkiness
- lose the bead head and go to a sinking line to get down