I promise you that if I ever make it 'across the pond', I will drop by, and you can tell me all about it whilst I oogle the many marvelous and magnificent boats that show up to your meets.
I've looked into the peltier a bit more and it might be possible to use them, especially on the exhaust steam from the engine. I think you would want the cold side to be cooled by water from the lake though. Keep the deltaT nice and high.
Even then, Producing 10w of power would be hard. A solar panel on the roof would work nice. And it would mean you could use the panel to trickle charge the battery and keep it up even when the boat isn't being used.
More to think about I guess.
A special section just for steam engines and boilers, as without these you may as well fit a sail.