I made it home and got the boat on the lift. The pictures below show the process of taking the lower end off of the Mariner to get at the impeller. The first picture is the bolt you have to loosen to disconnect the shift linkage. I lies under the rubber grommet that has to be removed first.
Lower unit removed
Four bolts hold the impeller hosing down over the drive shaft.
Impeller hosing removed
Here is a good video showing the whole process