I think it is probably him. I'm reasonably comfortable with the age difference as his death cert would put birth year at 1870, marriage cert at 1869 and son Leslie Herbert's birth cert puts it at 1872. So it's a little all over the place.
Hi Vickki
I think I would still treat this "find" (Kaipara to Sydney voyage), as a "maybe".

Sure, the "1895" ; the "C. St. CLAIR" and "London" perhaps have some significance, but I do wonder about the "age 20" ? (Would a chap really lower his age by five years ... and be paid a "boy's wage" ... although perhaps all A.B.'s were paid the same rate ?)
The thing is, with this departure from Kaipara ... is that he would have had to have come into NZ, sometime prior ?
So maybe the "ship-jumping thing" occurred in NZ ? And alas, no records available, nothing reported in newspapers.
Lu