"Robby" - Warren Raum and Ryp Siani

"Robby" is a low-budget Robinson Crusoe like film from 1968. It stars two relatively unknown actors: Warren Raum and Ryp Siani. Raum plays the 10 year old "Robby", a boy who has been stranded on an island. As he roams the island in search of food and shelter, and hopefully his parents, he comes across a naked native boy whom he names "Friday".

More info here.

Screen caps here.