ORIGINAL: DICKEYBIRD
It's hard to say without seeing it run but it sounds like your crankshaft is binding in the case. Either too tight mechanically or really gummed up with oxidized castor residue.
No, the crank is quite free -- perhaps a little too free :-)
I'm pretty sure I can detected some lateral play at the prop driver end :-(
And like Renegade, I was wondering how to remove the prop driver from the crankshaft -- is it simply an inteference fit or is it threaded?