I've always had male cats, and, have never had a problem with spraying. I don't know that neutering will change the smell of the urine or not, but, it usually will keep them from spraying. I don't know if it stops them from spraying if they're already in the habit of doing so. As far as I know, spraying is a territorial thing, and, I'd guess a male would be less territorial with just girls around. But, I could be way off on that guess. But, I think it really depends on the individual cat. I've never had cats spray or pee anywhere in the house other than the litter box. The most I've ever had at once was six. Boys and girls mixed. But, I'd just get him neutered as quickly as possible.