He appeared on the 1841 census, can't find him in 1851 and in 1861 his wife was shown as widowed. I have no idea what ship he was on at all.
Then that might be a problem. You do need to know the name of the vessel. Then you can find the Official Number and search the records at the Maritime history archive in New Foundland to see if they hold the agreements for that particular vessel in that particular year.
http://www.mun.ca/mha/http://www.mun.ca/mha/holdings/searchcombinedcrews.php I have no idea why they're held there. The Nat Maritime Museum here told me that it was decided that there needed to be one repository for such things, so they let them all go, except a small sample - agreements lodged in years ending in 0 or 5. Seems a bit mad to me, but what do I know - they wouldn't do it for no good reason now would they

But don't give up yet, you may be lucky and be able to find his name on a list somewhere - especially if he died off the Newfoundland coast! Actual crew indexes are few and far between online for some unfathomable reason (someone is missing a trick somewhere I'd say!). But, as you probably know, there are some at Find My Past (only a small percentage of what's actually available sadly) so you could try there. (they were originally available at CLIP, but FindMyPast bought them I think.
But your best bet is probably this this -
http://www.mun.ca/mha/publications.php#Newit's a little expensive, (which is why I haven't bought it yet

) and there's no guarantees he's listed, but you might want to give it a shot. (I have no idea why they've put it on cd rather than making it fully accessible online - what are we living in, the dark ages?

)
If you don't want to go to that expense just yet, I'd suggest, if it was a fishing vessel he was on, and you know it disappeared in Newfoundland waters between c1841 and 1861, I'd suggest concentrating your efforts on the newspapers. Losses were posted by Lloyds so you should easily come up with several likely names in the period. Then you can probably narrow it down further by eeking out all the unlikely vessels - or the most likely ones, such as those from what were his most likely home ports. Perhaps his name will pop up in one of the reports, or perhaps an inquiry may have been held...? That would give you a potential name for a vessel, for which you can find an official number, and then you're back to finding out whether the agreements are held in the NF archive or here, in the NMM.
I hope that helps. Regards, Ann