Topic: Resealing a badly sealed tank

[McQueen 750]

I have a rusty tank that was "sealed" by PO. Can I go through the normal POR15 process (Marine clean, POR15, then sealant) or do I need to do something special to get all this cracked and pealing sealant out?

[greenjeans]

I'd get the old liner out.   I had to do the same to mine and it was a pain in the arse.
What worked best for me was some aircraft paint stripper.  ** Make VERY SURE that the tank is vented if you use the stripper - it WILL build pressure if not vented.
After the aircraft stripper, I used an old bicycle chain and shook the crap out of it over and over.    I then used some "The Works" toilet bowl cleaner to get rid of the rust.  After all
that, I found that I didn't even need to re-line it.

Long story short, the better shape that the inside of the tank is before you coat it, the better chance the liner will work.