They definitely won't crow at 5 weeks. More like 15 weeks, but it depends on the guy. I'd say anywhere between 12-20 weeks is normal range for first crowing.
I think it can be tricky because marans cockerels are sometimes SO obvious, and sometimes not. First picture here is my BCM roo when he was 9 weeks. Also pictured is his sister (presumably) who died young.
Next is my pullet, Gretchen, when she was 5ish weeks and I was taking lots of photos...