I have never used the Moorings base in BVI, but in SXM, we arrive around 2 hours before departure time, so there is time to do all the final paperwork, check the boat, that everything is working (Personally check the water levels, and fuel levels) make sure charts are on board, etc. We usually get out of there within 30 mins of departure time, unless there is an issue with the boat. (Something not working, etc) When we arrive at 10am, I usually jump on board, and turn on the Fridge, so when we load food at 12, it is getting cold. A bag of ICE in the Freezer really helps to drop the temp quickly. Be nice and respectful to the staff, and they will go a long way to make your departure timely.
Not sure how this post started talking about GPS Navigation... Who knows!
If you have cruised the BVI many times, and are familiar with the area, then the chart briefing is not so necessary. The longest delay for us has been 1 hour after boat pickup... Crack a beer, read a book, and relax! If you are too rushed, you will be frazzled the first time you grab the helm, and that is when things go wrong! Enjoy your trip!