I've used butyl tape to re-bed hardware with good success in stopping leaks, but it's only part of the solution. I think you also need to over-drill the fastener hole, remove the core material around the hole, fill with epoxy, and then re-drill the hole. Use the butyl to prevent leaks. There are plenty of good articles written on this process.

Because of the design, materials used in construction, particularly vinylester resin, and workmanship, the e-27 will be around for several more generations, and you owe it to successors to try and preserve the core as much as possible

:: 4200 is close to as strong as 5200, but much easier to
:: remove later.
::
:: Also, I was involved in a restoration project on a
:: Morgan 42 last year and we used butyl. This year we're
:: already rebedding most of those fittings with 4200 FWIW
::
:: :: I have to add some hardware and replace some. I have
:: :: been reading about this and it seems that people are
:: :: using butyl tape to do this. Everyone cautions against
:: :: 5200 from 3M.
:: ::
:: :: Does anyone have recommendations? I think the SC27 are
:: :: done with the butyl.
:: ::
:: :: Thanks
::
:: :: Don