Installing Impeller on 1988 Evenrude 90 Hp

[Captain P L]

I recently purchased a boat with a 90 HP Evenrude and I want to install a new impeller but I am not sure as to where I need to look to remove the linkage so I can remove lower unit to expose the impeller. I have removed the four bolts on the lower unit but decided to ask for guidance before I make a mess. Thanks for any ***istance available, verbal directions or referal to a source for schematics that point out where I should look for the release screw.
PS: I am told that the Tilt and trim does not work, what should I check first.

[boats.net]

The shift shaft disconnects from top of shaft, remove the bolt from shift linkage underneath bottom carb.

[stratos]

its all in the mm

when in doubt allways turn to the maintenance manual. I have used these on my evinrude 200hp and they are awsome. tilt, try checking the fuse first.

[Captain P L]

Thanks to both respondents. I will take heed to your advice and attempt the repairs tomorrow, Tuesday 4/28/10 and will let you know of my success (smile).
Captain P. L.

[Captain P L]

Update to post

I found the bolt and as fate would have it I broke the bolt when attempting to remove it. I am really lost now. A friend suggested removing the carb so I can hopefully get to the broken bolt so that I can then remove the lower unit as planned. In the meantime I will order the manual on monday to see if that will give me any hope.
Any ideas - all suggestions appreciated,
Capt. P. L.