first of all you should disable all mods with jsgme. than, open your silent hunter 4 main directory aka "Drive/Programms(X86)/Ubisoft/silent hunter 4/. mark the "MODS"-folder and copy it e.g to your desktop. afterwards, uninstall silent hunter 4 and delete the main folder as well if it is still in existance. reinstall the game, install the uboat-addon if not installed yet and install jsgme. copy the "MODS" folder back into the main directory. make sure no other mods are enabled besides the "ALFA", which proper designation is "ALFA US_GE " link:
http://www.gamefront.com/files/21152569/Alfa_US_GE_zip