October 31, 2016   Karen Higginson

This is the How-To article from Alex and Jack Wilken, of Seattle Boat Works, from the October 2016 issue of 48° North.

This is the time of year when we need to think about what to do to prepare our boat for the coming change in the weather, this may mean finding and fixing leaks. We have all had them, and they do not discriminate – they come from above or below the waterline. Leaks can be deluges or seep so slowly that all you see is salt crystals building up in some area because the water evaporates at a rate faster than the leak. Leaks are not only inconvenient, but many times can cause damage to the interior or gear that gets wet. One of our boats had a leaky chainplate that corroded just below the deck level and broke due the constant wetting and drying. The source of a leak is not always immediately obvious because the water may enter at one point from the outside and travel before it enters the boat. This can require special gear or different methods to track down. Once you find the leak, you need to determine whether its fix is intended to be a temporary or permanent fix.

Recognizing that you have a leak is usually easy, but sometimes you will not know until you open a drawer and find everything in it swimming around. There are other telltale signs like varnish or paint bubbling or breaking down near the overhead or deck on the interior of the boat. Discoloration or corrosion on metal fittings like ports or chainplates, especially if a similar fitting does not exhibit this, normally means a leak.

Figure 1: Directing the stream of water, “A,” away from the suspected leak point, “B.” This is done by angling the nozzle, “C,” at about a 45° angle allowing you to have control over the leading edge of the water.

When you know that you have a leak, it is time to find the source. Over the years, we have used various methods and tools that work for leaks above the waterline. A very simple method involves a hose and two people: begin with the spray directed away from the site that you suspect and very slowly move it toward the area while someone watches from inside (Figure 1).

Sometimes using water will not be appropriate so you can use air pressure or a canned compressed air duster. Sprinkle baby powder or corn starch on the outside of the boat and use the duster on the inside. The compressed gas should find its way through the leak and disturb the powder on the outside revealing the location of the ingress of the leak. If compressed air is used, caution is needed to not cause damage from too much volume or pressure.

Figure 2: The ultra sonic leak detector has a transmitter “C” which, in this case, is outside the boat. The receiver, “A,” is connected to special headphones, “B,” to listen for the sound leaking through the channel that the water is using to gain access to the inside of the boat. Here we are verifying the leak’s location after having the transmitter and the receiver switch locations – transmitter inside and receiver outside.

There is an ultra sonic leak detector that uses a transmitter placed on the inside of the boat and a receiver with headphones to find where the sound is leaking through the same passage that the water uses to leak in (Figure 2).

Another method is to temporarily cover a suspected entry point with a bucket, tarp, tape or other method, and wait till it rains again. If the leak stops, you have your point of entry. One of the advantages of this method is that rain water can sometimes find its way in where hose water will not. We have used all of these methods successfully, but no method works all of the time or in all situations.

Leaks below the waterline are a different kettle of fish. The first step, if the source is not obvious, is to dry the bilge out completely. This can mean after the bilge pump has done its job you get in there with a sponge and then paper towels. This gives you the possibility to see from which end of the boat the water is coming and then follow it back to its beginning.

If it is a fiberglass or metal hull, you can start by checking all the hull penetrations. On wooden hulls, it could be a seam anywhere in the bilge. Stuffing boxes are at the top of the list, with thru-hull fittings right behind. And, if it is happening every time it rains and there is a keel stepped aluminum mast, the water could be coming down inside the mast. If you have keel bolts, they are a possible entry point, but, again, you will need to dry out the bilge to catch this one.

Keep in mind that not all leaks must be exterior. You often have water in your boat to start with. Water tanks and systems can leak as well, including when you fill them. On our boat we normally have little water in the bilge, but all of a sudden the high water alarm went off and upon inspection we discovered that the bilge pump was off and the bilge was full. We had recently left the tank filling and some of the water was going into the bilge from a leak in the vent line.

Figure 3: Fill the leaking area with Captain Tolley’s Creeping Crack Cure, “A.” In this case, the window frame created a trough that could be filled, “B,” to allow the sealant to seep into the leak. If Captain Tolley’s runs through the channel, then let it dry and change to something more viscous like liquid Boatlife.

There may be times when you need a temporary fix until you get back to your home port or until the rain stops. There are specific products that work in wet environments. Splash Zone and Boatlife Life-calk are formulated to be applied above or below the waterline. The other advantage of Lifecaulk is that, unlike many other sealants, water will not inhibit curing if it gets wet before it has time to cure. There are other products that have similar properties; these are just the ones we like. Usually you would squeeze the sealant into a crack or sandwich it between the boat and a bolt-on fitting like a stanchion or port, but in some emergencies you can get away with globing it on top or covering a leak.

Another temporary fix is tape. There are many grades of options for tape fixes, duct tape will come first to many people’s minds, and it can work very well. Gorilla Tape can do an even better job. We had a T-bird sailboat which had several leaks in the top when we got it that were kept dry with a temporary fix that lasted for seven years with black Gorilla Tape until we finally fixed the leaks and painted the deck. However, to waterproof the hinge, we reapplied white (to match the paint) Gorilla Tape, and as far as we know, it is still dry. There are also tapes that are designed to be applied to wet surfaces.

Figure 4: Tape off on each side of the area where you want to apply sealant, “B,” and then use your finger, “A,” to wipe off the excess sealant so that no buildup is left on the tape before you remove it.

If the leak is below the waterline, there may be enough pressure behind the leak so that even Splash Zone will not have time to cure without the water forcing its way past. In this case, use a piece of wood or plastic that is 3/8” or more thick and a little bigger than the leaky area. Use something to wedge the piece in place and you should be good until your next haul out.

Now that you have found your leak and are ready for the permanent solution, there are still options and tricks. Captain Tolley’s Creeping Crack Cure can be an excellent fix for small leaks where you can pool it at the entry point even if this means creating a dam with tape to create the pool (Figure 3, page 26). This milky liquid will seep into the channel and dry clear. Simply keep applying until it stops dripping. Check the inside during this process. If the liquid is running right through, stop, let it dry, and move on to the next, more viscous option, which is Liquid BoatLife. It is not as thin as Captain Tolley’s, but will work better on larger channels. It may be necessary to tape the inside to keep the sealant from running through. The other option is to recaulk with standard sealant.

Eventually the only real solution for a piece of hardware may be to remove it completely and reinstall. When reinstalling, it is a good idea to tape all around the fitting when you dry fit. Make sure you have an even coat of sealant over the whole mating surface so that you will have at least some of it squeeze out everywhere. When tightening the fastenings, make sure that the bolt/machine screw does not turn, and only turn the nut so as not to squeeze out all the sealant. One way to create a gasket out of the sealant is to draw the fitting close with the fastenings, but not tight, and let the sealant cure or partially cure. Now, you can tighten it all the way down. If you do this, it is even more important not to let the bolts/machine screws turn or you may break the seal. If there are sheet metal or wood screws, make sure to bed them well. When cleaning up, clean off as much sealant as possible before pulling the tape (Figure 4). Also, do not use solvent near the seal as it can work its way in and cause a leak.

So, you found the leak and you stopped it, but there are still other ways to deal with some of these situations. We wrote about tape that can go on wet surfaces, but there is also tape that can be used to seal hoses, or create mast boots. The thing that these tapes have in common is that they have no adhesive. They are applied by stretching them over themselves, and they stick only to themselves, acting as a single, molded piece. There are also alternatives to caulking and sealant such as rubber gaskets or butyl tape. We recently installed a port-light that used no sealant and does not leak.

Leaks can drive you crazy. We hope that some of the above cures will make your boating dryer and more enjoyable!

Jack and Alex Wilken are experienced boat builders and have cruised extensively. They hold USCG Captain’s Licenses and are the owners of Seattle Boat Works LLC in Seattle.