Sears Ted Williams 7HP how to remove lower end?

[rocstar]

I just got a free 1971 Ted Williams motor that has been mothballed for a long time. The model is 217.59480. I have been working through the motor to reawaken it. I have ordered a service manual on CD, but it hasn't arrived. I would like to inspect the impeller, and get a new one if necessary, but I can't get the lower unit off. It looks like (from the Sears web site and this forum) that I just need to take the screw out that is in the back, below the cavitation plate, and the nut that is in the front behind the clip. I've done that, but there is something holding the lower unit on in the front. There are no other screws in the sides except the fill hole for the gear housing.
How can I get to the impeller?

[CATransplant]

It's probably corrosion on the stud that nut behind the clip goes on. That's a pretty common problem. Try some penetrating oil, but don't use too much force. You don't want to break it off.