I tried your Facebook link and it didn't work. Can you upload them to this thread?
I don't know where you are thinking of using the ferro. If there is a problem with the steel
pontoons you may be better off welding patches over any area of thin plate. If you ask around there may be paints that do Ok on steel in the Murray.
If there is a problem with the superstructure then if the aluminium is Ok you may be able to remove it carefully, replace any damaged or rotten wood and replace the aluminium. Putting some foam insulation
in place may make it much more habitable.
It really depends on how much time and money
you have available for your project
Please be careful and think things through beforehand. From news reports the Murray can be unforgiving of mistakes