I can confirm that we have three lots of data for no ships, medium and large ones. 27 is the shortest RW we can use at BOS and the difference between no obstacles and the tallest ones is very significant in terms of limiting weights, engine thrust settings, flap and speeds.
If your takeoff performance was worked out for a clear shipping channel you could easily end up overweight or in the wrong configuration for the appropriate clearance if a tall ship was in your takeoff path.