Hold up!!
That's not a 7c4 Turm!, the 7c4 vintage boats 1944 didn't have a deck gun. Are you enabling the 7c4 addon and then selecting a 7c1?, I'm confused the 7c4 add on is men at for use when you have a 7c4 boat eg. late in the war4. You shouldn't enable it when you use a 7c1 boat.
Anyway, judging by the gun o the crane they're about to fit it for you
Regards
Aces