A Pulley Driven Drive Shaft

Any salty words of wisdom would be most welcome.
With a pulley driven drive shaft, such as Rob Whites rig on his Atkins based Rescue Minor, how is the forward thrust of the prop and therefore the drive shaft translated to the hull?
I spoke with some very nice folks at Grainger Supply today and they suggested running the drive shaft through a tapered pillow block. This is what Mr. White did in the RM (although he does not use the word tapered, only pillow or flange block). But the blocks they showed me mounted to the drive shaft with 1/8 in or smaller setscrews. I am sure two set screws are adequate to handle the rotational forces, but those rotational forces are sent to the prop which pushes the boat by translating that rotational energy into a linear force that pushes the drive shaft and therefore the boat forward or backwards. So two or four setscrews (depending on the number of pillow blocks) bare the entire effort of the motor, prop and running gear?
What stops the drive shaft from being pulled or pushed out of position by the prop? Just the set screws??? How is the shaft connected to the hull with out being connected to a trans/motor assembly? What is it that bares the load of the push from the prop into the boats structure? What is it that holds the shaft from moving fore and aft?
I am laying out plans to build an Atkins Patsy using a motor I already have that would require a pulley connection to the drive shaft.
Thanks, any help is great.
Jet

 

The bearings you will need have a locking collar, that is
eccentric. It is rotated to lock the bearing and shaft to-
gether, the set screws only hold the locking collar in place.

http://www.thebigbearingstore.com/servlet/the-50/1-dsh-1-fdsh-2"-Pillow-Block-Bearing/Detail

 

McMaster-Carr has a good selection of thrust bearings as well. Plain, ball, needle, sealed or open.

 

The coupler on a conventional setting is held by two set screws only. The pulley need to have an interference fit. A pair of thrust bearings in all you need. Marine transmissions have thrust bearings built in already.

 

Years ago I saw photos of something like your building.
They had a V-4 Diesel setting on top the shaft.
The Reduction gear was mounted in the bottom of the boat, secured to the shaft flange in the normal manner. So all the thurst is in the Reduction gear which is bolted securly.

They had a 4" wide, and pretty thick, Cog Belt running from the Shiv on the Diesel down around another similar Shiv on the front of the Reduction gear.
What caught my interest was the Cog Belt was not held in place by anything.
It was slid on from the front. There was an adjustable "carriage' that the Engine sat in which was lowerd in front to replace the belt, then the engine was 'adjusted' back into place and (I suppose) you then ran the engine with the Reduction gear in Nutral and adjusted the engine until the Cog belt ran true.
They said that belt would last a long time. Also the belt was a standard design for something else and would be available for a long time to come.

My experience with those 'V' belts on Riding Lawn mowers is 'aggrevating' to say the least.
There's also the Cog belts they use on Auto engines which run for thousands of hours.