I love dogs and I love sailing but, for me, the two just don't work together; but that is just me. Each to his own as they say.
There was a rather famous dog in Simons Town, South Africa called Just Nuisance. Simons Town was the Royal Navy's base near Cape Town and Just Nuisance was a great dane who ended up being enlisted into the Royal Navy. The story is rather interesting and can be found at http://www.simonstown.com/tourism/nuisance/nuisance.htm
Just Nuisance died towards the end of the second world war and so the name should be available.
I also read recently of a sailing dog named Fluke. Fluke of course is the working part of an anchor but the dog also found his new owners by fluke (chance) when they were berthed in Aberdeen, Hong Kong.
Whichever name you choose, I hope you and the dog have many happy years of cruising together.