One thing to consider is that occasionally you might have to leave him onboard when you need to go somewhere and it might be too hot too leave him in a vehicle while you are in a store or whatever. It gets hot inside a boat too and you'll need some kind of AC. I bought a portable unit that fits under the comanionway ladder. Only 7K btu, but keeps it tolerable. You would need shore power
of course to run one.
I agree that Pit Bulls are wonderful. I deeply miss my "Shadow" who passed away recently. Have his ashes on the boat. Decided on a Lab for my next dog because Pits are so very misunderstood and are not allowed in lots of places. Kind of like having a pet dragon. Also, they swim like rocks.