Well, here's what I've harvested from Kipling.org:

The Theme

Some sailors celebrate their safe return from a perilous voyage from Sunderland in northern England to Spain, in bad weather, in an ill-found, unseaworthy and over-insured vessel, by getting drunk and creating a disturbance. It is not clear if the owners intended them to be scuttled or overwhelmed by the storm, but they survived and brought the Bolivar safely into Bilbao.

The story is told with great verve and is neatly encapsulated by Lieutenant-Commander A.D. Roake writing in KJ 312/48. This is an extract:

Kipling's "The Ballad of the 'Bolivar' " is a poem for which I have a great "fellow feeling". He had done his homework as always. He knows his navigation too, going down-Channel past 'Start' [Srart Point in Devon – Ed.] and 'The Wolf [Wolf Rock,off Cornwall – Ed.], then south across the Bay of Biscay to Bilbao in Spain.

His reference to 'pully-haul' in emergency steering, the hogging and sagging as she pitches, and the 'plummer-block' (which takes the thrust) are all real technical terms. The 'greybeard' sea is also a term used in particular by "Cape Horners". 'Bluffed the Eternal Sea' also has meaning for me, and many other seamen. And there is the lovely bit of irony in the last two lines;

'Ain't the owners gay,
Cause we took the Bolivar safe across the Bay?'

Charley Noble