HI Dave, catching up a bit, just read your query, if all else fails try ringing Jerome at SHG Models a very good chap at solving problems and makes all his own parts. good luck

Model boat bits" make prop shafts to your spec. I've had a few 4 & 5mm inner shafts made to save changing the whole unit. Ring or email with length of tube. Then add a bit for "play".
Have a thread put on one end to a stated length(can be shortened later to suit prop) Then replicate coupling end.
Then all you need are threaded props.
Hope this makes sense

Thank you Doug, I've dropped them a message
Br Dave

Hi.
If all else fails, I would suggest you get in touch with Prop Shop, they do high quality brass props
from small MTB props to larger submarine props.
However they are made of Brass and not plastic, they are not cheap, but you are paying for the quality as he makes his own individually and at a price he will make individual props to your specification. I have dealt with him for many years and would highly recommend his work. He does a large range and also does a catalogue.
Hope you get what you are looking for.
Happy Modelling.
Doug Mayo.

HI thanks for reply, I think you're right but worth a try. Graupner couldn't help.
But yeah maybe a bush could work, I'm reluctant to change shafts as they look about right
Thank you !!

I fear that there is going to be a negative answer to your problem. To obtain replacements your best bet is to contact Graupner direct.

Failing that you could fix a length of brass tube over the end of your prop shaft and cut a thread into it so you can use normal props.