Hey'up Andy, have a look on the Model Boat Forum as I think I saw someone flogging a decent steam plant for a steam launch that looks as though it will fit the bill and look good to when on the water. Don't know if it is still forsale or how much, just that it looked the business for a large launch ok.
Link to is:
http://www.modelboatmayhem.co.uk/for...?topic=11121.0
Cheers
Wal