A Spenserian Master's Tale:

[Leanne]

For twenty years and more she made me vent
upon the rolling rooftops of the sea.
I shredded mainsail in my discontent
and broke her back or so it seemed to be -- would "seemed to me" work?

Ashore; I often paced along the quay--
a taste of briny spray upon my lip
and yearned for orders that would set me free;
to leave the harbour empty, in my ship.

Negotiate around Africa's tip; -- though it's not really wrong, "Africa" does throw the meter out just the tiniest fraction -- would it work for you if it were changed it to "Negotiate around the Dark Land's tip"?
or traverse winds along the Tasman Strait. -- again, "traverse" sounds a bit off but it might just be a difference in accent -- you could consider "or ride the winds along the Tasman Strait"
It never mattered where, or on what trip,
as long as we could float and carry freight.

It's all steam now, no need for canvas sails,
no need for dogs like me, no need for tales. -- really good couplet, very sad

As you can see, billy, just a few tiny little suggestions from me -- it's quite a lyrical piece and a good match of subject to form.