Just to report what i found out, i had started a career with S-Boat and I put in a 4.50 gun. I'm not 100% sure if it was the one on by default or I chose it... Bad research on my part
As I said before, it didnt work, was pointing down as if broken (same problem I had on Balao) and did not traverse.
So after 1st patrol, in dock I changed it to a 3.50, and voilá, now it's working!
I think my problem was just using guns not allowed on some subs, and so I could mount them but not use them. (I didn't have the crew problem, that part is well documented on TMO manual).