Wow thanks for the great response!
Some more details to see if any of the above applies:
The model is the Badger from Deans Marine and is around 36inch/1 meter long with the prop a 45mm brass 4 blade, make unknown.
The shaft looks like those from Deans with an oiler pipe fitted.
The shaft spins very freely with a small amount of play for and aft and has no indicated snag points.
I use extreme low oil volumes so as to limit the build up in the shaft.
The model has probably done around 10hrs of sailing with no other hitches. I know that the pool and lake are different in the water types, the lake having a large algae build up at this time. The model just goes right through the weed as if it was not even there.
Deans did show a 2:1 gear used on their build but as this was not available locally I did not use one. They also used a mechanical speed controller and I installed a Timaya type locally available.
The other project on the workbench presently is Branaren with a similar setup but the prop is a cast type with a lower pitch. It is certainly not as smooth running as the Badger on the water, but this is more to do with the hull types probably?
Trials showed this not wanting to turn at low revs and ended up with a new brass shaft as the steel one was found very rusted! seems to be going fine now, Why do suppliers give steels that rust as this will cause problems if laid up for a while?
Kevin