My 9 yr old son has yellow drainage and a smell coming from his ear?

Needs evaluation: This could be as simple as putrefied wax draining after getting wet or may represent a draining ear infection. Only an exam can tell for sure.

Followup: Your son may have an ear infection. There are outer ear infection which usually drain but a middle ear infection can also rupture and drain. Your son should be seen by his pediatrician because he may need antibiotics.