If he is three, marking is already a learned behavior. Neutering him won't stop him from marking. However, I would still get him neutered. Have you tried a bellyband in the house? It is a miracle for me! One of my dogs is a twelve year old Cairn-poo.....he has been neutered since puppyhood, and he still marks!! If I didn't use a bellyband on him, I would have strangled him long ago!
