It was not uncommon for crew to desert once they arrived in South Australian ports. The library has South Australian deserters indexes to those who deserted between 1852-1876, 1877-1882 and 1883-1890 (available on microfiche). For full details of individuals who deserted their ship, you will need to go to State Records SA.
As these men were contracted to the ships, desertion was classified as a criminal offence and warrants were sworn out against them. From 1862 onwards more information may be found in the South Australian Police Gazettes.
Finding details of ships' crews can be very difficult. Usually official records of crew no longer exist.
The State Library has some resources which may help:
Manifest of vessels arriving [in South Australia] from overseas 1838-1842 [microfilm] Includes crew names. (Also known as 'Inward manifests to South Australia ...)
SA Pioneers arriving 1836-1845 - Source 27-36 Lists compiled in the former South Australian Archives from various sources, includes crew names.
Manifest of shipping departing from Port Adelaide, list of crew July 1841-May 1844 [microfiche]
H.M.C.S. Protector crew lists South Australia's first naval ship. Two lists - one undated and one for 1901. (Research Paper no. 855)