Is it needed to get a 2 year old purely outside cat neutered?

Yes, have him neutered. It is the only responsible thing to do. If he does belong to someone else, well, they aren't taking care of him, but it is highly unlikely, as he showed up on your back porch starving. We have the same issue. An extremely affectionate male cat, still intact, that we have tried to get to the vet for neutering, but not having any luck capturing him....he is an escape artist when it comes to getting him in the truck to get to the vet's. We even resorted to a live trap without any luck too. I now have an extremely affectionate porch cat, still intact, and limping on three legs. He was in a vicious fight and his leg is now broken, and I still can't get him to the vet to have it set. Fortunately the infection is cleared up, and hopefully someday soon he will be able to walk on all fours again. I can't imagine how much discomfort he is in and how many kittens he has spread out all over the county. Have yours neutered and don't regret a moment that you did.