Hey guys, Is the distance between the back of the motor to the u-joint critical (seems like the shaft is kind'a long...LMAO) and how much shaft should be sticking out on the prop end?
I'm rebuilding an old go-devil (the 9-13hp model I think) and putting a 18hp engine on it. I will get some pics up tomorrow evening.

Take a tape and measure from the yoke collar down the length of the drive shaft tube, note the length where the shaft would exit the tube (accounting for the extra length added from the bottom seal cap)... after that you just have to account for how much you will need for threads... might be best to refer to the go-devil manual and see what kind of hardware (nuts, prop, washer, ext...) they use on the bottom end of the shaft, this info will let you know how much you need for threads... 3/4" cold rolled round stock cut to length machined for a key on the engine side and threads on the prop side is a great option ($25-$35) vs buying and shipping from go-devil...