corrosion df6 longshaft

[chrispy]

hey hey... i have a df6 longshaft from '05. when i went to remove the lower unit, the nuts came off easily enough but the lower unit will not slide from the mid unit. the aft stud seems to be solidified to the first inch or so of the lower unit.
lots of penetrant, shocks with mallet, gravity, heat, all to no avail. corrosion from hell.

[boats.net]

There is no easy way of getting it off, we have in extreme cases drilled a hole through side of housing and through stud to cut stud into, then have hole in housing welded up.