Rusty Bilge in Shower Area

[TheSaintlyOne]

So obviously priority is to get a thickness test on the Hull but noticing in the area that used to house the shower/sink area the steel is particually flaky. But appears there may have been some sort metal  sump tray/liner  that has rusted away as the flakes are quite large in so much as that they peel away to leave the main cross beams looking completely in tact and a solid floor underneath. Was this a way of building dumps when the boat was made in the 70s or do I likely have a thickness problem. Rest of the bottom is bone dry 

[David Mack]

The rust is about 10 times as thick as the parent metal it has come from. So that should give you some idea of how much thickness of metal has been lost.