Following from the death index entry found by
neb_maat_re Reply #6
Not much help, but at least it means he's still in the running...........
PROV has a will for
Alexander BOYD, of 521 Victoria St, West Melbourne,
Railway guard, died 24 December 1894. Bequests to his wife, Sarah Jane and to his children - unfortunately not named except for the eldest, who is the executor of the estate: Hugh BOYD. There is no mention in the will of the name "McKeller", and his forename is listed as 'Alexander' rather than the 'Alex' on the death index entry. He signs his name as 'A Boyd'
As you have already found the death index entry states that he was aged 48 at his death which fits quite well with the birthdate you have given.
This is possibly the marriage for this man and Sarah Jane
Victoria 1873 # 2044
Alexander BOYD
Sarah Jane BURROWSSomeone with better resources may have a birthplace listed for this man.
I see 4 births to this couple - if it is your man none of the names except for Hugh seem to follow the usual Scottish naming pattern which may mean something, or nothing

Hugh, 1874, reg Melbourne; father: Alexander McKellar BOYD
Allen 1875, reg Footscray; father: Alexander BOYD
Elsie, 1882 reg Hotham; father: Alexander BOYD
Sarah Alice, 1883 reg Hotham; father: Alexander BOYD
Perhaps this is this man's immigration:
Sep 1870, per ship Colonial Empire from Plymouth to Melbourne
Alex C Boyd, 23,
rly guardEstimated birth year: abt 1847
Nationality: Scottish
Unassisted - i.e. paid full fare.
http://prov.vic.gov.au/provguide-50As I said - just a possible

Judith