Did this the other month to replace the impeller. Look up and google impeller replacement, because it tells you exactly how to remove the lower unit. Anyway, there are two bolts to remove, one is difficult because you have to ease the lower unit off as the bolt is removed (I used a small scraper to get into the seam of the upper/lower unit. takes some time but nothing is holding it in from the inside as you were thinking. Make sure the shifter is in nuetral and do not move the "shaft" once it is out!! It has to go back in the same way. Good Luck, Have patience.