[yorkietalkjilly]

I would confine him in a crate or small pen when I couldn't be in the room to watch him. Clean the peed-on areas with the special biological cleaner and then you will just have to be certain he can't re-mark until he's better housebroken after the neuter. I think it might take a few months before a lot of the marking urge will leave him after that so you will just have to keep taking him out very, very frequently to get the message across that he will always have ready, frequent access for "going" outside, watching him very closely when he is out of his crate/pen to prevent marking, confine him to his crate/pen when you leave the room or home and hope that in time he will get the idea that the better place to mark is outside for all the world to enjoy his wonderful scent. But I suspect that since he's marked so much all over the house, he will have to be closely monitored for repeat performances for at least another year or so until the urge and his memory/scent of where he should re-mark are lessened and hopefully gone altogether.