I Have a 3 yr old neutered male who has recently started urinating on the floor. What can I do to stop this.?

We have 3 indoor cats (2 neutered males and 1 spayed female) who all get along and have lived together for over 1 1/2 years, and 5 outdoor cats (4 males 1 female)that we care for. We have an oversized litter box that is cleaned daily. He normally uses the litter box. But sometimes he will urinate in the same select places in the house. I can't have him urinating in the house and I wanted to get rid of him, but my wife says that if anything happens to her cat, I'll be the next neutered male in the house. Please Help.