Deaths of passengers are noted in the ships manifest (passenger list)
Sometimes the death is noted beside the name - with a date and sometimes a cause.
Sometimes the deaths are all recorded at the end of the passenger list.
To find a death, you need to get the passenger list and go through it carefully.
and scroll down to the link to "Abby Land 20 Dec. 1850 Liverpool to New York "
You can look at the images online and see how the deaths were recorded on that voyage, as an example.
Olive Tree Genealogyhttp://olivetreegenealogy.com/