taking in the 14hp surface drive shaft in tomorrow to get threaded and am getting confused.

I have a 3x4"-10 thread but on some post I see that you want a right handed thread shaft, although I have a hill marine 10x8, (left hand thread) My motor turns ccw.

I'm looking at the following schematic and wondering, what thread direction i need to have

Does the prop torque on the rear jam nut or the forward jam nut when in motion and to alleviate the back pressure when the prop hits a log so it can spin back slightly on the other jam nut,
what jam nut does what

the washers and jam nuts will have the opposite threading to prevent it from coming off?

Don't worry about all that. If your prop and motor are correct then you know what thread direction you have to go with. There's nothing you can do about it.

Don't all the majorSDs have thr prop float in case it hits something & slightly loosens?

You don't say....