We have a male (approx 10 months old) natural Papillon who routinely wets on himself (chest and front legs) when he is let outside to potty. We have 2 other dogs in the house, a male neutered Chihuahua (2 yrs old) and a female, spayed retriever mix (approx 1 yr old). Neither of these other 2 dogs have ever had this problem so I am not sure why or how the Papillon is doing this. Would it stop if we neutered him or is that even a factor? He is pretty well housebroken (a small accident here or there) and he does "mark" everything around the house.
Any advise would be great!

Getting him fixed is just generally a good idea. Sounds like what our male poodle does, he is really clean in the house but when he goes outside to go to the toilet he ummm... isn't a good aim... he tends to miss the grass and wee on his front legs. When he was in show coat we used to put waterproof boots on him just made of fabric with elastic at top and bottom.
I don't know if that would be very practical for you but if he only goes outside at certain times to wee it might be a thought :)