Re: Bedding Deck Hardware With Butyl Tape
I would use it anywhere above the waterline where the item is bolted in place. I don't think an item attached with screws can always compress it enough. It can be dissolved by fuel as well.
If attaching wood or to wood I would make sure the wood is sealed and not bare. Varnish, paint, or ideally the wood is epoxy sealed first, as it probably should be anyway for longevity.
Living aboard in Victoria Harbour