Can You Build Your Own Power Boat? 
Having grown up in a third world country, the concept of a marina filled with boats and yachts was, well just that – a concept. It's only when I moved out that I discovered that, one of the joys of the developed world was DIY kits for everything – even a boat! Besides, there is also the option of constructing your own boat right from the beginning. 
The focal point of consideration in a power boat is the hull. The type of hull will dictate the kind of activities you can do in the boat. The reverse is also true; what you want to do with your power boat should guide your choice of hull – for example, you will hardly expect high speed from a trawler (heavy displacement hull). And if it is a high speed pleasure boat you're out to make for yourself, the hull will be sleeker and will be lighter in terms of displacement (planing hull). For this type of boat though, be prepared to shell out more money for the expensive engine and high fuel cost. Another wonderful option is the twin-hull catamaran; ideal for long cruising as well as for speed. 
The material for the hull could be wood, fiberglass, aluminum or steel – take your pick. The boat kits come with various options – you could simply assemble all the pieces together or you could obtain the boat design and partial kits and build the rest yourself. For example, you could assemble the hull from a kit, or get the design and have it cut locally. Similarly, you have the choice of assembling or constructing the bulkheads, deck, rudder, superstructure and so on. 
So really, you can build a power boat in your backyard. Just prepare yourself for some investment – monetary and otherwise.