Your boy isn't even old enough to breed yet and far from being fjull grown. you don't know how big he will be when he is done growing.
I would suggest to you to get him neutered now, before he reaches puberty, or he will be lifting his leg all over your house for the rest of his life.
If neutered before they reach 7 months, most males do not mark in fact many don't even lift their legs. But once they reach puberty it becomes instinct and you cannot prevent it.