Bulbapedia doesn't have surfing information for RBY Route 4, and I don't trust the wild Pokemon tables on this site. Please don't question my curiosity.
I have been surfing around for a quite a while, and I am encountering nothing, so no.
You can't encounter wild Pokémon while surfing at Route 4 in RBY, you CAN receive a lvl. 5 Magikarp and in further generations, you get Pokémon by Surfing.