There are training sprays that worked great for my dogs, I have a Yorkie and a Jack Russel and it worked for both of them. It is called Potty Training Aid it train pets where to urinate. It works for indoor and outdoor use. You just spray it where you want them to go and let them smell it after you spray it. Repeating, do the same routine over and over is how dogs learn to do something. Just keep the same potty routine and he should pick up on it..If you think you want to try the spray you can find it on
www.carealotpets.com Simple Solution potty training aid....You said he was too big to be a Yorkie, well some Yorkies are larger. I have one that will be about 10lbs full grown, that doesn't mean that he is not full stock if he is big..There is just more of him to love......