311 is an 81 with new mounts and at tickover the thumps raise the coachroof & you can watch the winches dance and your vision is blurry if you are properly barefoot. It would be interesting to see the two different J/30's you refer to. You might have the best persepctive on it. Engine mounts can be replaced. They are mounted on big glass stringers, and that may be the point of improvement across model years.
