You can do 1 of 2 things. 1) remove prop, use a socket that will slip over the crankshaft and rest against engine housing, tighten prop nuts until crannkshaft is reseated. or 2) ship to horizon for warranty repair. This happened to my evolution 26 cc and
i opted for #1. then about 2 weeks later I called horizon and notified them of what had happenned and they had me send it in for repair. I got the engine back in 2 -3 weeks along with a listing of parts that was replaced.. The same problem is also happening on the MVVS 26cc.