Hi Jean
You can get some information about the ships including the ID number from the Miramar index:
http://www.miramarshipindex.org.nz/I have had a quick look and found the following, which may be relevant.
Year M discharged - Ship name - ID number - type of vessel - tonnage - year launched - shipyard
1900 - Sea Fisher - 1083992 - cargo - 274ton - 1883 - Belfast
1900 - Black Boy - 5611985 - cargo - 537ton - 1854 - Jarrow
1905 - Langdon - 1085122 - cargo - 1262ton - 1882 - S Shields
If you have his discharge certificates you should have a "Discharge Number" and I think this should be unique to him.
All this information should lead you to a good knowledge of his maritime experiences and also give some additional pointers to his age and origins. It can be expensive to get copies of crew lists and I think you need advice from someone more experienced than me.
There is an informative Rootschat thread at
http://www.rootschat.com/forum/index.php/topic,385954.0.htmlHmac, one of the contributors to that thread, is very knowledgeable and may be able to guide you in this maritime research.
All the best
Gobbo