We installed our "Cheap Chinese (Webasto Style) Diesel Heater" on our 1963 Chris-Craft a year ago and it was an absolute life-changer for us as far as comfort through the winter on our very inefficient old wood boat. In addition to awesome on demand heat, as the heater is completely 12v, we were able to stop running all of our electric heaters and almost completely absolve our 120 system from the constantly pegged 30amp usage that kept tripping our breaker. No more shutting off the water heater to run the microwave or hot pot etc! This unit only uses a couple amps to run, and completely off the house batteries.
Installation is actually really quite simple, even on a boat like ours. I believe I've walked through and covered and of the 'issues' I had, but if you have any questions, please feel free to ask!!