Help needed

[White Star]

Hi all, i could really do with some help. Had a friend of my mums pop over this weekend and upon him spotting some of my white star line bits he proceeded to tell me about his father who served as an engineer on white star line ships, he then asked me if i could find out what wsl vessels he served on. Unfortunately all i have to go on is his name and the dates he would have been in service, his name is Richard Davies and the dates of service range from the 1920s to 1930s, thats all we have as his father died when he was around 3 years old. Any tips on how to find crew lists would be greatly appreciated. Many thanks in advance.