Re: Mud motor bearing/bushing housing questions.
Just buy a bearing set up from Backwater. But to answer your question you will need a 3/4" shaft with a 1/4" key way cut on one end and 3/4"-10 thread on the other. Keep all your threads outside of your seal/bearing assembly so that the threads don't cut the seals and the seals fit tight on the shaft. Most of the companies have gone to bearing setups on the upper and lower shaft assembly but you don't have to. Go Devil used bronze bushings on the bottom for a long time but they filled the shaft with grease to take the whip out of it and keep water out of the shaft housing. If you go with a bearing set up, accommodate the lower and upper setup for a couple of lip seals and alternate their direction to keep water out. Water in your shaft housing will rust your bearings and freeze. On a small hp long tail I would not fill the shaft tube with grease because when it gets cold its hard to start because of the friction of thick grease so you might need to put a center bushing in the shaft housing. You can build a shaft with DOM tubing but it will need shaft stubs welded in to use the keyway and prop. Most people don't realize that a solid 3/4" shaft whips like a noodle at 4000 rpms. Good luck with your build and your finding out they are not as simple as people think they are.