Repairing Inflatable Pontoons

Larry Tullis


Inflatable pontoons are generally durable but not indestructible so this article will cover how to repair and service your pontoons, rafts and other low-pressure inflatables.  Knowing how to repair your inflatable is important because of the time and trouble involved with sending it back to the factory, store or repair facility.  You may be on your boat for an important trip or vacation and don't want a lack of repair knowledge and repair supplies to ruin it for you.

There are two types of repairs: First is it a manufacturer or material defect and is it generally detectable the first time or two the boat is inflated.  This includes bad stitching, seam welds coming loose, fabric defects, leaky bladders or valves.  Always pump up your pontoons long before a trip to determine if they need repair.  Keep them inflated for 24 hours.  Large leaks will go flat immediately but small leaks and seepages take time to detect.  Small leaks, those that allow the boat to go soft in 24 hours, can be ok for a trip but should eventually be repaired.  Ideally, use the boat on a small local trip before taking a new untested boat directly to a longer, more important trip.

The second and most common type of repair needed is from user or accident caused damage.  This may include: over-inflation with compressor or because of heat and/or a sharp rise in elevation, knife punctures, sharp glass slashes, melting from fire or ember, unusually sharp rocks, oyster beds, hook punctures, spiny-ray fish punctures, damaged valves, excessive abrasion, animal tooth and claw damage etc..


Finding Leaks

·         Valves are the first things to check on leaky boats unless other damage is obvious.  Dribble or spray some soapy water around and in the valve.  Any expanding bubbles or continuous small bubble trails indicate a leak.  While the valves are usually quite durable and seldom break, they can leak if not tightened properly or if the valve seal gets dirty.  A valve wrench (special for each brand) is required to tighten or remove valves although needle nose pliers can be used in the wrench slots in emergencies.  The valves are two part and screw together like a jar lid and will leak if not tight.  To loosen the valve you may need to inflate the pontoon rigid, and then use the wrench to start loosening the valve, then deflate to finish unscrewing.  If the valve is tightened and still leaks, then the valve needs to be loosened and re-seated more evenly on the fabric.  You'll need to grab the inner part of the valve through the pontoon fabric as you tighten the outside.  Tighten fairly firmly by wrench and hand then inflate pontoon and finish tightening with the wrench.  If the valve bubbles from the center, it means a dirty or damaged valve seal.  Use a Q-tip and while holding or locking the valve open, swab the seal surfaces to clean.  Then fill pontoon with air and check for bubbles with soapy water again.

·         Big leaks are usually easy to find once pontoons are aired up, you'll often hear or feel the air coming out.  On boats with bladders, you may need to zip open the shell and pull the deflated bladder out (leave the valve intact) and re-inflate.  If you can't hear the leak, it may be a small puncture or bladder seam leak. 

·         Small leaks are harder to find.  Use soapy water to find the small leaks that will bubble.  If you have still water nearby (pond, lake, pool, trough etc.) you can inflate the pontoon or bladder and roll it slowly in the water and carefully look for air bubble trails in the water.  Mark the hole with a pen.  Keep looking for other holes, such as in the case of cactus thorn damage.  Once found, empty the pontoons of air to begin repairs.  Once glue is applied, don't put air back in until you are sure the glue is completely cured or the air pressure will make the patch fail as air is forced through the soft, uncured adhesive.


Repairing Leaks

The two most important things to remember about repairs is to 1: clean and prepare the surface of the fabric to receive any adhesive and 2: to let the adhesive cure long enough to be effective before adding any air or using the pontoons.  A knowledge of each type of repair method is needed to do it properly so here are some of my favorites.


·         Instant Patch Tape

Several brands are available and all work somewhat as temporary patches.  Although considered temporary, they are quick and easy.  Even high-tack duct tape will work but may leave a residue when removed.  They work fine for small incisions and punctures but are not good for large gashes or blowouts.  Tape is also good as a backing for other larger repair methods, to hold the edges together until the main repair dries.  Follow each brands instructions carefully.  In general, clean the surface with alcohol wipes or MEK and allow to dry before applying the tape.  Cut the patch to cover the damage and 1/2+  inch beyond.  Carefully peel backing from patch so as not to get it wet or dirty.  Apply to the damaged area and press firmly.  Burnish it with some semi-rigid but smooth item like the edge of a credit card to get any bubbles out and to maximize adhesion.  Instant patch tape is better and perhaps permanently effective to repair bladders and skins from inside pontoons because the pressure of the bladder against the pontoon skin helps keep it in place.  Tape is temporarily effective on bladderless pontoons but not good to keep air in forever.

·         Aquaseal

Aquaseal (McNett brand) urethane adhesive is ideal for many repairs because it adheres better than most glues and applies thick and in essence creates its own clear patch.  The downside is that for best repairs, you need 24 hours for the glue to cure.  You can use Cotol-240 accelerant mixed in to reduce the cure time to 2 hours and it is often sold in kits together.  Accelerant reduces strength a little but is still better than many adhesives.  Other brands of urethane repair adhesive such as Shoe Goo may work too but is not as good as Aquaseal in my opinion.

Clean area and possibly roughen area first with sandpaper.  Punctures need only a dab of Aquaseal smaller than a dime.  Slow seam leaks may only need a small wipe of Aquaseal.  For large cuts in the fabric, use tape to hold the back edges together, then make sure the pontoon is laid flat on a flat surface.  Apply a bead of Aquaseal 1/4 inch or more over each side of the slice or puncture.  It becomes smooth and may slowly flow downhill so keeping it flat is important to avoid drips.  A second, wider coat or another inner bead may be called for on large repairs.  Bladder boats can be glued inside and out and I have repaired huge tears up to 3 feet long this way.  Bladderless boats cannot be glued on the inside so a second, wider outer coat may be called for.  I glued some bladderless pontoons with 10 knife slashes in them (from a vandal) and although the scars are very noticeable, the pontoons are quite useful again instead of trash.

A polyester fabric patch can be used with Aquaseal to strengthen the repair even more.  Use a small brush to apply Aquaseal to the repair area and then to one or both sides of the fabric.  Apply the pre-sized fabric over the repair area and paint on more Aquaseal over the fabric, making sure there are no bubbles under the fabric.  Masking tape can be used to mask off areas around the patch area for a more professional looking repair.  Just remember to peel the tape off before the glue begins to harden.

Aquaseal now has a UV cure that is applied in the shade and when exposed to the sun it cures in 30 seconds, which may make it the best shoreline repair material on the market.  It is still not as durable a repair as regular Aquaseal but much quicker to get you back on the water.  At night or on cloudy days, the UV cure may not work unless you have a special UV flashlight to make it cure (found in some stores that carry UV products).  As always, clean area first with isopropyl alcohol pad (found in first aid sections of pharmacies), Cotol 240 (sometimes packaged with Aquaseal) or MEK (available at paint stores) to remove surface residue and clean the fabric, roughen the surface with sandpaper or a clean rock.  Apply UV adhesive in the shade with a clean stick to maximize adhesion, then add some more if needed to thicken patch.  Bring into open sunlight and allow 30-60 seconds for the sun to cure it.  Be careful not to get it on your fingers because it will burn somewhat while curing.  Also replace the UV Aquaseal cap while still in the shade.  Apply regular Aquaseal over the patch, covering a wider area later when you have more time for permanent patch.

Aquaseal can also reinforce worn areas.  If you've drug your boat over too many rocks and worn down the outer layer of the fabric, fix it by cleaning it properly, drying it completely, masking the area off with masking tape, sanding any smooth areas and painting Aquaseal on with a paintbrush or popsicle stick to create a layer of protection.  Aquaseal or another similar, thinner product called Seamseal can also be used to reinforce stitching in the skins of boats with bladders.  Stitching is the weak point of this type of boat and sealing the stitch line with a thin strip of Aquaseal or Seamseal will help stabilize the thread and protect it from abrasion.  If used on the zipper stitching, make sure it doesn't get on the zipper teeth themselves.


·         Glue and Patch Repairs

Traditional inflatable repairs use special contact adhesives and raft fabric patches.  You must generally know the fabric type you're patching and get special adhesives made to match them.  For example, many types of glue are not made for the PVC (vinyl) commonly used on pontoon boats.  Hypalon, PVC and Urethane are the main embedded fabric coatings you'll find in pontoons and rafts.

Prepare the surface by cleaning with alcohol or MEK (best) and roughening the patch surface with a rasp, motorized rotary tool/sander or sandpaper.  Follow the instructions included for each type of glue.  Usually you'll put down one layer of glue on each surface to be glued (boat and patch) and allow them to dry completely.  Apply a second coat and allow to dry only minutes (consult instructions for actual times) or until the glue is just dry to the touch.  Line up the patch and the patch area carefully because once it contacts, it is stuck quite securely.  I like to roll the patch on to avoid trapped bubbles.  Quickly use a roller or heavy hand pressure to assure a good seal with no bubbles.  Allow overnight to complete the cure unless in emergency situation.

This type of patch is done on the outside of bladderless pontoons and usually on the inside of pontoon skins with bladders.  Done properly, it is the most durable way of patching or reinforcing large tears or slashes.  It is also the way to reinforce high abrasion areas.


·         Seam Leaks

Although seam leaks in bladderless pontoons are generally considered manufacturer defects, you may want to easily fix them yourself rather than sending them back and not having them to use for a time.  Inflate the pontoons tight and find the leaks with soapy water, then mark them lightly with a pen.  Clean the area with alcohol or MEK, let dry and apply a thin layer of Aquaseal on the seam.  Allow it to dry 24+ hours before putting air back in.  Small leaks can be endured without patching while on a trip, just keep a pump with you to top off the pontoons as needed.

If the welded seam of a pontoon has a flap that is coming loose, glue it down with a quality waterproof contact cement after cleaning and drying the surfaces.  Once glued down and dried overnight under a heavy weight to insure adhesion, I like to add a small bead of Aquaseal to the seam for extra strength.


·         Blown-out Stitching

Stitching that is being rubbed and frayed or UV damaged on bladdered boat shells can be stabilized with Aquaseal or Seamseal.  Make sure none gets on the zipper.  Most blown-out stitching occurs from excessive rubbing (such as between wheel wells in a truck bed) or from severe over-inflation with air compressor or in hot sun or transport while inflated from low to high elevations.  Also from those who leave boats out in the sun year-round and get UV damage.  Stitching already broken should be stitched up professionally by a tent, awning or upholstery shop with heavy-duty polyester thread.  Emergency stitching can be done using a hand awl with a sharp needle installed and waxed twine or HD poly thread.  Be careful not to puncture the bladder while sewing.  If the shell blows but the bladder is intact, use duct tape or gorilla tape to temporarily hold the shell together.  Remove tape ASAP to avoid messy tape residue, then repair properly.


·         Bad Repairs Redone

I see numerous bad repair jobs that need redoing because they still leak.  Usually it's from not cleaning and preparing the surface properly before gluing or not letting the glue cure long enough before airing the pontoons up again.  Use heat (heat gun or hair dryer) to heat and help loosen bad patches.  You may need to grind down glue clumps with a Dremel type tool and mini-sanding drum.  Once smoothed and cleaned with MEK, Cotol 240 or isopropyl alcohol and sanded, re-apply glue and/or patches properly and let it cure long enough to reach full strength.


Repair Kits

Pontoons are tough and resilient and the wisdom of seasons teaches that you won't need a repair kit... unless you don't bring bring one.  In over 1000 days on the water in pontoon boats, I've honestly only had to repair one boat during a trip when an Alaskan grizzly decided a boat was a beach chew toy.  However, I've repaired many people’s boats that have damaged them in dozens of ways.


·         Complete pontoon repair kit:  Gorilla tape, instant patch tape, boat material patches, contact cement (made for your pontoon material), sandpaper, alcohol wipes, Aquaseal, Cotol 240 (accelerant and cleaner), MEK, Aquaseal UV, UV flashlight with extra batteries, copies of instructions, high volume hand and 12V pumps, pump to valve adapter, small spray bottle with soapy water, napkins, small disposable paint brushes, popsicle sticks, roller, valve wrench, spare valve, sewing awl, pressure gauge.  Separately Zip-loc potentially messy items.

·         Basic on-board pontoon repair kit:  Gorilla tape or instant patch tape, Aquaseal UV, UV flashlight and extra batteries, sandpaper, alcohol wipes or Cotol 240, napkins, a compact pump.  A weeklong trip may include some more of the complete kit items.  Each kit is different and the user needs to decide what to bring for a particular trip.  Some users bring only patches and glue.

·         Other items you might consider (non-pontoon related items): Extra oar, extra oar-lock and pin, wire, bolts, washers and wing-nuts, spring pins, extra pontoon, extra cam straps, multi-tool with pliers, pressure gauge etc..


Care and cleaning

Pontoon boats generally don't require lots of pampering but you'll lengthen its useful life with these following hints:

-Rub them down with 303 Protectant once or twice a year.

-Don't drag them much, if any over dry, abrasive or sharp objects.

-Scrub off dark rub marks with Comet and a wet pot scrub pad...if you care about looks.

-Pontoons and rafts only need 2-3 pounds of pressure so monitor pressure.

-If you let a boat sit in the sun or you go over a mountain pass, the air pressure will increase quite a bit.

-Keep the pontoons soft until you are ready to put it on the water then top it off with a few pumps from a good hand pump before using.

-Remember that cold water will shrink the air volume inside the tubes so over-pump slightly in the morning and let some air out at lunch as air warms or if your tubes get drum tight.

-Dry tubes thoroughly before rolling and storing them, especially tubes with bladders.

-Keep sand and grit out of the area between skins and bladders and out of valves.

-Secure assembled boats to vehicle or trailer with 4 cam straps to frame corners instead of bungee cords or motorcycle tie downs, both of which can easily fail.

-Check and re-check tie-downs several times during a trip with a boat inflated.

-Keep metal parts from making pinch holes in bladders when transporting boats broken down.

-Avoid the need for repairs by avoiding things that can damage the pontoons.  It sounds simple but requires vigilance.  For example: check for thorns, cactus, barbed wire, broken glass etc. before dragging a boat on-shore.

-Avoid hitting bridge abutments or broken cement riprap that may contain sharp edges or metal projections.


Most of all, go have fun on the water!