Well actually from the west side of the island to San Pedro is inside the reef as is Caye Chapel. The blue hole is a much longer trip which is outside the reef. Depending on where you are on the west side you will need to have a shallow draft boat considering in some places there is not more than 6 inches of water.

Anytime you want to make longer trips such as the blue hole you should consider having two engines and going outside the reef is better suited for a deep V hull you are going to have a hard time finding a boat that will be able to handle both the inside and outside very well. In my opinion you are better off looking at two boats.