usually getting a male cat fixed before they start to spray will eliminate or highly reduce the possibilities of them spraying. In your case that didn't happen. It may be because he started puburty and have nothing to do with being neutered. If you have stray or outdoor cats that come in your yard and spray or leave they're sent he may be spraying because he wants them to leave. If that's the case you'l want to wash places that look or smell like they have been sprayed and also work on keeping other cats out of your yard. Also if you have more than one cat you must make sure each can get away from each other if necassary and each has it's own food litter box (although they still might share) and toys. If he is new he may just do it for a short period of time. If none of these seem to be the problem you should look at other posts concerning how to stop spraying and look at other websites regarding this behavior.