As I posted on that other forum, the new twin cylinder double acting marine steam engine from PM is great. I just built one of the first. It is a pre-machined kit, and is only $159. Very sturdy, not delicate like my Graham TVR1A. It is so new that if you want one you have to call and ask about one, it's not on their website yet. Shown here on a chunck of wood so I could run it. Ran first on air, then on steam. Single control gives variable forward, reverse and stop. Quiet and smooth. 1/8" shaft already has a flat machined for a coupler. Now to find the right boat...