Getting the wrong sub for a new boat, in particular a Tambor, is a known issue with TMO 2.5, but there is a fix that Aanker worked out in cooperation with Ducimus, here's the link:
http://www.subsim.com/radioroom/down...o=file&id=3506
This is a small mod that will fix the incorrect progression for getting a new boat, but it also disables the Terrible T campaign, so if you want to play that, disable the patch.