"Hi, hopefully Bob will come b
"Hi, hopefully Bob will come back and help more on this one! Yes, it has to be measured from the top of the bottom lower unit on the inside. Being you have not had it apart and if you have not turned the shift rod, might not need to adjust it. But if you do want to make sure it is correct, I am sure it has to be seperated as I could not measure mine with them together. If it is adjusted too far one way, will have forward and no reverse, too far the other way, no forward and just reverse vise versa. As touchy as these drives are to be exact measurements, now is a good time as the bottom unit will not seperate from the top attached to the boat. Maybe someone can jump in here to advise to adjust it or leave it as is?"