Home › Forum › Ask A Member › Can 1955 mark 25 lower drive unit fit 1956 mark 25 › Re: Can 1955 mark 25 lower drive unit fit 1956 mark 25
If you wish to install a 1955 lower unit on a 56 and later tower, you will have to either change the shift shaft bushing/holder, (it threads into the lower unit and keeps the shift shaft in place and seals the shaft) The diameter of the bushing is larger in 56 and later. It will also have smaller hole in the housing for the rear bolt as they switched from a 5/16" stud to a 3/8" stud. You will either need a very thin walled socket or need to enlarge the relief area around the hole where the stud goes through to get a socket on and of course drill out the hole in the lower unit to fit through a 3/8" stud.
Steve