since its used to encapsulate electric cables I would think the waterproofing is ok when bonded to itself,but bonded to painted/GRP surfaces?Dont know.Also UV?Again,dont know.I got offered a deal on some and wondered if it was akin to butyl tapes,the 3M info doesnt really say enough to tell.
I bought a roll for a couple of quid.I dont think I will chance it on major seals but it will come in handy on inside fixes.I will post results of trials.......