I've just taken a 68mm prop with 70mm steerable nozzle off mine, because I wanted the motor for my new Tyne Models Northsider, I can't get hold of this particular motor anymore.
I've now put a 50mm MMM kort on now, because it was lying in my box, the 70mm was a bit over the top, but not really a problem, ideally I think the 60mm with the MMB 900 will be good, I've just ordered the MMB755 for mine, hope to have it fitted Wednesday so will post how it goes.
This is the link to my Nangee build, a recent posting, but the boat was built 4 years ago, still got it despite a number of people making 'offers'. Its a very good boat for tug towing, I would only sell it if I decided to do the Portgarth or Afon Wen, itds not too big, and you can get enough power in it no problem.
http://www.modelboatmayhem.co.uk/forum/index.php?topic=22158.0Andy