Hi Bill,
Just saw your post and question. I just acquired the old version of the Amsterdam (All wood) my plan is to use a car seat motor from Princess Auto $10 hooked up to a 1/8" square shaft to any U joint that does 5mm to 4mm (these are many), I'm also changing the rudder to a Kort like the original and replacing the propeller. The motor I mentioned using 12v will move it along very well and will provide both power and durability plus the balast bonus.
Hope this helps.
BTW I'm your neighbour in Burlington, so maybe we should arrange for a meeting and discuss further.
Hany