If you're strictly talking boats, I would say you need to be knowledgeable of engines and 12 volt electronics... especially if you want to be a captain. Otherwise the little you make in profit will be spent on mechanics. It seems as though something always needs tinkered with or serviced. You shouldn't buy a boat without a good survey. Personally, I think Captain Tony surveying is the best. He will find anything and everything. This should make you aware of any problems and help you negotiate a price. A big block inboard will need rebuilt around 4000 hours, keep that in mind. I would suggest an inboard, there's just less that can go wrong. Like Jim said, give him a call, he's very knowledgeable.

Greg