I responded to your question on another forum, but I got to thinking that you might check that there isn't any
trash, or metal shavings in the spinner nut. That's unlikely, but still worth checking 4 Stroke engines typically
use larger props then 2 stroke counterparts. Larger props have thicker hubs, and that's the reason your shaft
is a little long for your spinner. You might call the manufacturer and explain your problem, and they might have
a solution. They might have a special short nut, or they might modify one for your application?