This topic has certainly come up before. There is some discussion, for example, in the thread Stan Hugill's Performances . Probably some others, too. However, I did not find a dedicated thread.

The following is a DRAFT of something I am working on, a short statement on the topic. I am aware that Mudcat member, and maybe some others, has thought a lot about this. My thoughts come in the context of a wider discussion, in which I am trying to address this issue fairly briefly.

One of the assumptions in that wider discussion is that there is such a thing as a "core" repertoire and/or paradigm of the chanty genre. Not everyone will accept that assumption, but you need to be aware of it for my interpretation to make sense.

Anyway, here are the drafted thoughts - on which I welcome comments and criticisms.

(Embedded footnotes to references, and some formatting, like italics, are missing.)
***begin excerpt***

It is clear that chanty lyrics were often mundane, yet potentially witty at other times and, therefore, entertaining. Were they "dirty"? Some degree of bawdiness has come to be popularly associated with sailor culture, yet we must remember that chanty-singing did not belong exclusively to sailor culture either. Moreover, few specimens of dirty lyrics survive in the published literature. Still, there persists an idea that sailors' lyrics would have been very often obscene, sometimes along with the corollary that obscene lyrics must be more authentic. Historical statements on this issue are conflicting.
        At one end of the scale, we have the statement of Williams, the American sailor of partial African descent, who denied there being any obscenity in chanties.

>>Another thing is that, while many of these songs have stood the test of a century, or perhaps two, and have passed from lip to lip thousands of times over the airs to which they are sung, they have never changed. Still another somewhat remarkable fact is that thruout the whole list of known chanties there does not occur a single offensive word, and whenever any indecent language has been injected into one of our favorite chanties, it is at once expurgated by common consent. <<

I have included the remarks at the beginning of this passage because they seem so implausible. The songs "never changed"? Despite Williams' considerable experience, the statement sounds like wishful thinking and so his denial of indecent language, too, sounds incredible. In fact, the very "proper" English captain Whall said quite the opposite.

<<…seamen who spent their time in cargo-carrying sailing ships never heard a decent Shanty; the words which sailor John put to them when unrestrained were the veriest filth. <<

However, he continues,

>>But another state of things obtained in passenger and troop ships; here sailor John was given to understand very forcibly that his words were to be decent or that he was not to shanty at all.    <<

While this does not quite explain Williams' unfamiliarity with indecent chanties, it suggests the possibility of different norms in different spheres of activity. Moreover, obscenity, while present, was expressed with a strict sense of proper time and place. Yet another viewpoint, of non-sailor Terry, seems to argue that context was more or less irrelevant since only solo lyrics would contain bawdiness and these would not be heard at any significant distance.

>>The Rabelaisian jokes of the shantyman were solos, the sound of which would not travel far beyond the little knot of workers who chuckled over them. The choruses—shouted out by the whole working party—would be heard all over the ship, and even penetrate ashore if she were in port. Hence, in not a single instance do the choruses of any shanty contain a coarse expression.   <<

The last statement of Terry was famously contradicted by Hugill, who offered the example of the chorus to "Jamboree": "Jenny, keep your arsehole warm!" There is also Hugill's chorus to "Sacramento": "There's plenty of grass to wipe your ass on the banks of the Sacramento." These, however, seems to have been alternate forms of the choruses that, while known to Hugill in his time (1920s-30s), were not necessarily standard earlier. It may be that sailors became more obscene with their chanties as time went on.
[cont.]