Mounting or "humping" behaviors are usually dominance behaviors, and not sexual. It's common among both sexes as well as among dogs who were spayed or neutered before 8 weeks of age.
But two weeks is really not all that long in terms of the presence or absence of hormones in the body. Did this behavior only start since he was neutered, or did he always do it?
Beck was neutered at 4 months and now, at 15 months he has started humping. I asked the Vet, she said in her opinion it is not really 'dominance' related but is a display of excitement. She said that dogs still produce sex hormones in their adrenal glands after neutering, just not as much as are produced in the reproductive system.
I can see that - Quinn is not dominant at all, and never humps other dogs. But when he's really wound up from playing with us, he'll do it. Then play time is over. :)
Oh the days of humping! lol We had a Lab that was fixed at 6 months but humped up until the day he passed away. I LOVE having a girl and that was one of the reasons I wanted a girl. It was too embarrassing to see the "red rocket" and have little kids say "what is that pink thing"? Sorry, I don't think there is an answer or cure to this question.
My two guys (now both neutered) consider "humping" a sport. Some Doodles do really well at agility, or flyball, or even dancing....with my guys it's all about the humping. Murphy actually is pretty good at it....Guinness, not so much. Sometimes he does it from the front, other times from the side, he's just not sure exactly how to go about it. I always watch their ear and tail positions, and they're usually just playing and excited. If I see any signs of one trying to dominate the other (versus taking turns and just "fooling around"), I immediately stop it. When I say "knock it off", they usually stop because they know the one I catch first will have a little "crate time out". Usually it's just "boys being boys", but once in a while it feels like a dominance thing, and then I do end it. They have never humped an object...it's always each other. I really wouldn't worry too much about it....believe me, there are "way worse" things he could be doing.
We had a little female terrier, who was spade at 6 months, but all the other dogs were big. She would get very excited, trying to play, and if she didn't get enough attention, she would also hump...but on their heads or leg or whatever she could reach! It was quite funny, as the larger dogs never paid any attention to her behavior, and she'd get tired of it after while.