Re: I have a 1972 6hp johnson
That's sort of correct. There is a pin through the top end of the drive shaft. That pin has to come down through a slot. So, remove spark plugs. and slowly rotate flywheel till the pin aligns with the slot and the gearcase will drop down enough to disconnect the shift rod. When you get the lower unit off, note the position of the pin so you can put it back the same for reinstallation. Do not rotate the flywheel again till after the motor is reassembled.
It is NOT necessary to remove the pin from the drive shaft to remove the pump. Simply pull the shaft out of the lower unit once the pump is loose. Don't worry, it will go back in, no matter what you may have been told.