"you also need to be sure to level out the new mastic so the rail sits flat. otherwise it will leak again. " This is supposedly why C&C used butyl tape as their "caulking". Inherently flat and even, so if the bolts are torqued down fairly evenly, the seal is more reliable. In theory. Everything depends on the extent and nature of the leak. When the options include $40K I think I'd consider all the alternaives first, inclduing some baffles and a drain
line to the bilge. (G)