K1W1 : , shaft tube, stern tube i really don't know how its called
but i have seen it work, I think this idea was picked up from some boatbuilder in Stuart, there have been like 5 boats that have done this modification and all of them picked up some speed, im looking to do this myself next month when my boat is hauled..
Spinnaker : don't know what a shaft brush is
, but I will do a search thank you......