I would like to ask if the above would be ok to use as a shaft for a home built longtail. I plan to build a 6.5 hp and need some advice. I plan to use a 3/4 inch shaft but I am not familiar with different types of steel, and what I find on the net is kind of confusing to me. I am a fair welder and have access to most of the material needed for the build. Last but not least let me say I have read every article on the longtail talk forum and really appreciate the attitudes and advice given.

i have used the 1018 on long tail shafts before up to 16hp and have not had any issues at all, it has a tendancy to lightly rust more than the other types but i did not have any problems with it.
we use it for axles on carts we build and it is pretty tough

1018 will probably be ok for a small motor like that. Most manufacturers use 4140 which has a yield strength about 3X that of 1018. I have used 17-4 H1150 Stainless on the motors that I have built. It has a yield strength at or above that of 4140, it has corrossion resistance and it has a tight diametrical tolerance (.750" material is +/-.002")

Mag10