For those who doubt the utility of butyl tape on boats, and who chose to use polyurethane products such as 5200, for installing ports, this photos speaks for itself.
As you can see, after nearly 30 years the butyl tape still had elongation before break of more than 2000% at a minimum. The butyl tape on all 8 ports never failed and my leaks were from Beckson port gaskets, even after replacements had been installed.
I also had a couple of fasteners, that went through the foam weather stripping gasket used on the trim ring (not butyl), also leak.
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