I'll give you the same reply I gave someone on another site with the same question.
you would be darned lucky to find a houseboat wiring diagram. Anyway boat wiring is boat wiring. The principles are the same whether it's a houseboat or a power cruiser. I suggest you take a look at

http://newboatbuilders.com/pages/elect.html That will tell you the regulations and lead you to the section on DC systems and AC systems. (Basic Electricity)

There are also some basic wiring diagrams at the bottom of the electrical page.

There are some good books on electrical systems.

Boating Magazine's Powerboater's Guide to Electrical Systems by Ed Sherman
Boatowner's Illustrated Handbook of Wiring, by Charlie Wing
Your Boat's Electrical System, by Conrad Miller and E. S. Maloney
Boatowner's Mechanical and Electrical Manual, by Nigel Calder
The 12 Volt Bible, by Miner K Brotherton and Ed Sherman

I would suggest Ed Sherman's book or Nigel Calder's

If you have specific questions ask them and we'll try to help. I would strongly suggest that when you get into the AC wiring you hire a certified marine electrician.