I have spent most of my working life in the boat trade & have seen a lot of penetrating epoxies used on old boats. It is marketed as a cures all ills panacea & many people get sucked into this idea.
It has its uses but for large items like boats it very rarely works & in fact often causes far more problems than if the boat had been fixed properly in the first place.
The prime example was a 40ft motor yacht built by Morgan giles in the early 60's, she had spent most of her life on the upper Thames & on coming down the tideway was hauled on the slipway at the yard i worked because of some persistent leaks. She had been treated extensively with Git Rot penetrating epoxy. It hadnt worked & the rot had spread far & wide. We ended up taking out & replacing half of one side & bottom before the owner ran out of money & called it a day. At that point we just patched her up as best we could to get her afloat.
Three days later she sailed for Calais via Ramsgate & disapeared. An extensive air sea rescue found her tied up on the river swale her owner having omitted to tell anyone of his change of plan.
None of us who worked on her forgot that queasy feeling wondering if she had sunk on account of us not being able to finish the job properly.
Penetrating epoxy = Snake oil.