Using a Pontoon Boat in Salt Water: Tubes, Anodes, Flushing, Rinsing and Copper-Free Bottom Paint

Your boat builder and engine maker may have specific rules for salt water use, required anodes, approved paint and flushing. Some limit warranty coverage for salt water damage if the steps aren't followed. BoatUS's freshwater-to-saltwater article says to check and follow the manufacturer's warranty instructions before you start using the boat in salt.

Avalon lists three things it recommends for pontoons used in salt water, each a dealer service at extra cost:

• Antifouling paint made for aluminum on the submerged parts (step 3)
• A barrier between the tubes and the trailer bunks (step 10)
• Anodes on the boat, if the dealer recommends them (step 5)

It also recommends a yearly inspection for corrosion and for deterioration of the electrical connections, and states plainly that Avalon and Tahoe do not warrant saltwater corrosion. Avalon suggests asking the dealer about construction details that suit salt water, such as tubes fully welded to the deck structure rather than welded every foot or so.

A Mercury Dockline article on saltwater pontoons describes what builders' saltwater packages typically add: sealing the keel and other hull openings against salt water and barnacles, a sacrificial anode for the aluminum, and upgraded stainless and other materials; one builder adds a water-separating fuel filter for humid climates. A builder quoted there says its protective tube coating suits boats stored out of the water, while boats in full-time slips also need a painted barrier coat. Ask exactly what your package includes, in writing.

This is the mistake that can ruin a pontoon. International Yacht Paint (Interlux) says antifouling for aluminum should not contain cuprous oxide, because the high copper content leads to corrosion. Paints using cuprous thiocyanate are more compatible, but only over the correct primer system at the right film thickness to keep paint and aluminum apart.

• Kept in the water: Avalon recommends painting all submerged parts with an approved aluminum antifouling. Boating Magazine notes ABYC wants aluminum boats to have a protective coating that acts as a high-resistance barrier between the aluminum and the water.
• Trailered and rinsed after each trip: growth has no time to take hold; ask your dealer whether paint is worth it for you.
• Never let a yard use "regular" bottom paint, and never paint straight onto bare aluminum. Read the label: it should say it's for aluminum. If a previous owner used copper paint, get advice from the paint maker or a pro; it usually has to come off.

See our bottom paint and aluminum corrosion guides.

Boating Magazine describes how a Florida builder that markets boats for salt water isolates hardware and stainless bolts from the aluminum with nylon washers, adds dedicated anode brackets and uses thicker metal. When you add a ladder, cleat, fish finder bracket or anything else:

• Use quality stainless (BoatUS notes 316 corrodes slower than 304) with nylon or plastic isolating washers.
• Bed fasteners with a marine sealant so water can't sit in the joint.
• Don't leave sinkers, coins, bottle caps or loose hardware lying on the deck or in the tubes' crevices.

Anodes are metal designed to corrode instead of your motor and tubes.

• Never magnesium in salt. Martyr, an anode maker, says magnesium anodes aren't suitable for salt water because they corrode too quickly. BoatUS says to switch freshwater magnesium anodes to aluminum, or zinc if aluminum isn't available, when moving to salt.
• The outboard has its own anodes; follow the engine maker's alloy recommendation.
• Tube or hull anodes: Avalon says some boats need anodes added to prevent stray-current corrosion; ask your dealer. Boating Magazine notes there's no formula for how many you need at first; it takes some trial and error.
• Inspect at least every month or two in salt water. BoatUS says to replace anodes yearly or when they're more than half gone.
• Don't paint anodes, and make sure each one has bare metal-to-metal contact.

Anodes that disappear in weeks, or never wear at all, are a warning sign; see our aluminum corrosion guide and have it checked.

Kept in a slip for weeks at a time? Look under the waterline regularly, not just at the anodes. A 2026 notice from the Canyon Lake (California) property owners' association, written after many reports of pitted pontoons in its marinas, described early corrosion as rough bumps or small white nodules on bare or scratched aluminum. Its reports came mostly from boats left in the water for long periods, and only from aluminum pontoons, not fiberglass boats. When it inspected a marina, the stray voltage it measured above the docks dropped noticeably once privately owned battery chargers were unplugged from dock outlets. That was fresh water; salt makes every one of these problems faster. Don't run household chargers or extension cords on the dock, and if your marina's tubes are pitting, ask for an electrical check. Many owners on salt water skip the long in-water stay altogether and use a lift or dry storage instead.

BoatUS says outboard owners in salt water have to flush with fresh water every time. Two ways:

• Built-in flush port: many modern outboards have a garden-hose fitting. BoatUS describes using it at the dock with the engine off and the motor tilted out of the water, typically for 5 to 10 minutes (a Mercury pro's saltwater tips suggest at least 15 minutes on Mercury's flush port, again without running the engine); check your manual for the exact time and motor position (some makers want it vertical).
• Flush muffs: clamp external muffs over the water intakes, turn the water on fully before starting, and run the engine at idle only, with everyone clear of the prop. Never run it without water flowing.

Then rinse the outside of the motor and spray a corrosion inhibitor under the cowl if your engine maker recommends it. Our freshwater flush and saltwater outboard care guides go step by step.

Discover Boating says to rinse a pontoon with fresh water after each use, especially in salt, because salt speeds corrosion and leaves a white residue on aluminum.

• Pay attention to weld seams, brackets and crossmember joints, where dirt and salt collect.
• If you can, lift the boat slightly (on a lift or trailer) to rinse the bottoms of the tubes, where algae and scum build up most.
• Use a garden hose, not a pressure washer; Avalon advises against pressure washing on its boats.
• Clean oxidation with a cleaner made for marine aluminum. Discover Boating warns against harsh acids like muriatic acid, which can streak and weaken aluminum. Avalon warns against acetone, thinners and gasoline, which strip paint.

Salt spray settles everywhere on a pontoon's big open deck.

• Hose down the deck, rails, fence panels and furniture with fresh water. Rinse soap off completely.
• Avalon says vinyl gets a warm, mild soap solution with a soft brush, then a full rinse and air dry. Carpet gets vacuumed routinely, with deeper cleaning at the end of the season; remove all soap residue or stains come back.
• Lift cushions so the seat bases can drain and dry.

See our pontoon deck and furniture care guide.

Avalon is emphatic: salt water areas are usually hot and humid, so the boat must be dry before you put on the mooring cover or seat covers. Covering it wet means mildew. Once dry, a cover keeps salt and sun off.

Avalon warns that without a barrier, corrosion can start where the trailer bunks touch the tubes. Carpeted bunks soak up salt water and hold it against the aluminum. Ask your dealer about the barrier they recommend; Avalon pairs this with antifouling paint on the tubes. After a salt launch, Avalon also says to flush the salt water out from between the bunks and the tubes with your hose (it adds this doesn't prevent corrosion on its own if the tubes have no antifouling barrier). Owners rebuilding bunks are often warned in forums not to use pressure-treated lumber against aluminum, because the copper-based treatments in modern treated wood can corrode it; ask the trailer maker what wood, carpet or polymer bunk material to use. Inspect the bunk contact areas whenever the boat is off the trailer, and replace soggy or torn bunk carpet (see our trailer bunks and rollers guide).

• Rinse it after every launch. BoatUS recommends doing it within a few hours of leaving the ramp, even stopping at a car wash on the way home. If you use a car-wash wand, Mercury's saltwater cleanup tips say to keep the high-pressure spray off the wheel hubs, where it can disturb the bearing grease.
• Brakes: BoatUS suggests a brake flush kit that connects to a garden hose for drum brakes, and notes disc brakes are generally easier to flush with fresh water.
• Aluminum or galvanized frames still corrode. BoatUS points out that an aluminum trailer's bolts, nuts and spring hangers may be steel, and that any nick in a galvanized frame lets corrosion start.
• Bearings and lights: salt water gets into hubs and connectors. Check bearings, use sealed or protected bearing systems if your trailer allows, and use dielectric grease on light plugs. Our trailer guides cover each job.

BoatUS says to wash aluminum hardware regularly with soap and coat it with wax at least twice a year, and warns that most marine aluminum hardware is anodized, so many polishes will strip that protective layer. Avalon suggests waxing the aluminum tubes and side panels every three to six months. Look over battery terminals, switch panels and wiring connections for green or white corrosion; Avalon recommends a yearly inspection of electrical connections.