I am new to MMT and have started a build on a 14hp vanguard to put on a 12ft starcraft. I planned on putting brass bushings on the prop side of the shaft but was questioning whether or not to do so on the engine side. And also, how should I seal the ends? Could i use a 9x5 prop and be able to run less rpms and same speeds as a 8x4 or 8x5? Great site!

You'd be better off spending a little more money and putting a needle bearing at the top. Regardless of whether you use a bushing or bearing, you must make sure the driveshaft is centered inside the bushing/bearing. Use the Go-Devil owner's manual on their website to figure out how to make sure you're centered. Oil seals on each end and you should be good.