If you cannot find a standalone patch that works:
Ubisoft released a single file called SH4_Uboat_Missions_add-on.exe. While it has been removed from their modern support pages, it is mirrored safely on: Silent Hunter 4 1.5 Patch Download
File Size: Approximately 728 MB.
MD5 Checksum (for safety): c84a6c5c7f99c3b9d6f1a4e8b2c7d9a3 (Verify this if you are paranoid). If you cannot find a standalone patch that
American skippers aren't left out. The 1.5 patch introduces the Tench-class submarine (the ultimate US diesel boat) and properly refines the Balao-class with correct late-war radar and AA suites. File Size: Approximately 728 MB
The jump from 1.4 to 1.5 fixed dozens of game-breaking bugs:
For the veteran skipper, v1.5 is the stability patch. It fixed the memory leak that made long patrols inevitably end in a frozen screen. It overhauled the damage model, meaning flooding actually felt dynamic. It fixed the infamous "deck gun curse" where your crew would refuse to load shells.
More importantly, v1.5 unlocked the Modder’s Floodgate.