Scott and Brittany, aboard s/v Asante, rebedded their ports using a mixture of butyl rubber tape and 3M UV 4000 as a belt & suspenders approach to keeping out the rain. Here's how they did it:
Leaks. They are, quite possibly, one of the more (if not the most) annoying malady to befall the cruising sailboat. If they are below the waterline, they can prove catastrophic (as in; your boat can sink). If they are above, they can be madness inducing, teak-tweaking and gear-ruining. Lucky for us the leaks we have had have always been topside, and - even luckier - their origins have always been obvious. There are plenty of accounts of leaky boats who's sources are nothing short of a mystery. It is not unusual to see water coming into, say, an aft hanging locker - only to trace it all the way to a poorly bedded cleat up on the bow days, weeks or months later. Water, being what it is, has a way of migrating before entering the interior of the boat and playing detective in this regard has been known to cause some cursing.
Speaking of bedding (and, no, I am not talking about the new queen set that you found on overstock.com), the majority of topside leaks will come from poorly bedded deck hardware. For those who have no idea what I am talking about, the art of "bedding" deck hardware is mounting and installing it to the deck. Cleats, portholes, chainplates, stanchions..etc. Don't be fooled though. This is no small task! There are literally hundreds of holes drilled into our deck for various pieces of hardware which means there are hundreds places that water can potentially enter our boat, so the job must be done with painstaking care. Nothing will make you curse the previous owner of your boat more than discovering what a crap job he/she did bedding deck hardware and, for better or worse, the attention they paid to this crucial job is pretty indicative of the way they maintained their boat.
So far, our only leaks have come from our portholes (aka 'windows') in our cabin. We need to re-bed about six out of fifteen. I have mentioned before that being a full-time boat mommy has pretty much nixed my ability to help with boat work (dang!) but one thing I am still very, very good at is research. When investigating the best bedding compound, I discovered (and kind of fell in love with - in a deep respect sort of way) "Maine Sail" of Compass Marine. He is all sorts of awesome and his site is full of how to do a litany of boat projects the right way. It was through him I learned the beauty of Butyl Tape.
Scott got to work removing our old porthole, and discovered that it was bedded with the dreaded silicone. Silicone SUCKS. Say it with me people, "silicone sucks" and, in our opinion, has no place bedding deck hardware. After spending a few hours painstakingly scraping away all the silicone remnants, he epoxied the inside of the window cavity (so that if any water gets in, it's not absorbed by the core) applied the butyl tape around the edge of the porthole, and wedged it in. He then - for good measure - applied some 3M 4000 UV to the outside casing of the porthole and put the thing back together. Between the epoxy, butyl tape and 4000, we are 100% leak-free (and yes, it has been put to the test!)
Since we're far from experts, that's about as step by step as I want to go, but if you are curious about using butyl tape to bed your deck hardware the proper way*, please check out this article.
*There's more than one way to skin a cat and I am sure plenty of you have leak-free boats that swear by other products, but for us butyl tape is the way to go for bedding deck stuff from now on.
The role of butyl tape
Scrapey McScraperton. This is the most annoying part of the job for sure.
So it helps to have a very good friend around for moral support. Ben Affleck and Jake Gyllenhal in the Hiz-OUSE!
Applying some butyl.
Peek-a-boo! Clamping the porthole into place.
The outer edge of the window was sealed with some UV4000.
Tools of the trade.
Look, ma!! No leaks!