I've found a Felix Smith (born circa 1840) living at Boston Ward 12, Suffolk, Massachusetts in the 1870 US Federal Census. He is not the only Irish Felix Smith, but the only one of the right age. He was living with Margaret Smith, born circa 1847 in Ireland, and Chas Smith (1867), Ann J Smith (1810), and Elizabeth Smith (1869) all born in MA, indicating that he probably emigrated to live with relatives, certainly for a time. Margaret was almost certainly his wife.
To prove that these are the right records you need to trace forward from as early in his life as possible. If you know his parents' names and his birthplace that would be very useful. Search the UK and Ireland censuses from as soon after his birth as possible, eliminating all the records that give the wrong year of birth (if more than 3 years out - only age at the time of the census was recorded, so birth years are uncertain) or the wrong parent / sibling names. This way you should be able to follow him around the country.
Try next to locate the Dacian in records (there is nothing on Ellis Island immigration records, so it probably didn't dock in NYC) because the ship's mainfest will tell you a great deal about who he travelled with (if anyone), and most importantly his intended destination. The you can start looking in the US census records, starting with his intended destination, and once you know where he was living you are more likely to find his death record, and naturalisation record if he was naturalised. (This is because US records are split into states in most cases).
A good place to look is ancesty.com - instead of signing up at a monthly rate you can pay �7 and access records for a 2 week period. For this price you can use the search engines and see the results, only viewing the original documents costs you credits, so shoebox them and on the last day before your credits run out view them all at once (you can then save them to your computer).