Serial numbers from 3931 to 7500 are 1923.
The cast tank Johnson’s have a strong interest
in the hobby. Your LU is in better condition than
most. An indication your motor has been well
cared for. If you want to disassemble it any farther
you should remove the pump first. Don’t want to
beat this fastener thing to death but the rope
starter screws are the ones most likely to have
been chewed up and are really hard to come by.
They are way to small to be used with a puller.
Here is a link on how to remove the flywheel and
one with some history on the early Johnson’s you
might find interesting.
Tubs
https://youtu.be/RWgE9XiIBnk
https://www.yankeeaomci.org/johnsonat85.htm
.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.