Some reference info.

Back in 2008, I put together a chart of the items in SfSS. Based on that, I tallied the "items" in SfSS at:
418

This, no doubt, is where the book jacket gets the figure, "over 400." (However, it seems that note may just be on the Mystic Seaport Abridged edition -- which really only has closer to 280 items.)

Here, "items" includes any text that is given its own heading, and any melody variants. So for example, "Rio Grande (A)"and "Rio Grande (B)" would both be counted, i.e. 2 different items. The item count does not include little scraps of partial texts (though it includes partial melodies, if they differ from the main item).

If one collapses variants -- eg. if both the Rio Grande variants are considered as one piece of the song repertoire -- then the total number of items (or songs, let's say) is reduced by about 118.

The totally number of "different songs" in the collection, then, is close to 300.

Hugill's later books, SHANTIES AND SAILORS' SONGS (1969) and SONGS OF THE SEA (1977), add about 5 English-language songs (I don't have the exact count by me!) and a few foreign-language songs.