Pontoon Underskinning (Underpinning): What It Does and When You Need It

Pontoon underskinning is a layer of thin aluminum sheet fastened under the deck to cover the crossmembers between the tubes. Builders and dealers also call it underpinning, an under-deck skin or a wave shield. This guide explains what it does and doesn’t do, which builders offer it, and how to fit or inspect it.

It is written for US owners and buyers deciding whether to order it, add it later or accept a used boat without it.

What Is Pontoon Underskinning?

Pontoon underskinning is a set of aluminum panels screwed or riveted to the underside of the deck crossmembers. It turns the open ladder of channels between the tubes into a smooth, closed surface that water slides past instead of striking.

On a standard pontoon, the deck sits on full-width crossmembers, often Z-bars or C-channels, bolted to brackets on the tubes. At cruising speed, water thrown up between the tubes hits the bottom edge of every one of those channels. Sun Tracker describes the skin as metal sheeting that covers the Z-bars and gives “a smooth surface and significantly less resistance”.

Coverage varies by boat. A partial skin covers only part of the underside. A full skin runs from the bow to the stern and from tube to tube.

Is Underpinning the Same as Underskinning?

Yes. Underpinning and underskinning name the same thing: aluminum panels covering the crossmembers under a pontoon deck. Sun Tracker uses “deck underpinning”, owners usually say “underskin”, and Harris lists “skin kits”.

The Sun Tracker learning center calls the same panels “deck underpinning” and “under skinning” on one page. Sun Tracker’s 2021 catalog lists deck underpinning as a feature of its XP3 models, next to three 26-inch logs with lifting strakes. “Wave shield” is a third common name that owners and dealers use for the same under-deck panels.

What Is an Underpinning Kit for a Pontoon Boat?

An underpinning kit is a set of pre-cut aluminum panels and fasteners sized for one pontoon model. It is the factory skin sold as a package rather than sheet stock you cut yourself.

Kits come from the boat builder through its dealers, or from a metal shop that measures your crossmember spacing. The kit does not sit under or on top of an existing skin. It is the skin.

What Does Underskinning Do on a Pontoon?

Underskinning stops water from slamming into the crossmembers at speed and in chop. That cuts drag, reduces surging and keeps spray off the deck underside, wiring and steering cables. It does not add buoyancy or stability.

What builders and owners report it does:

• Cuts drag: Harris says its skin kit “reduces drag and surging caused by water hitting the cross-members”.
• Smooths the ride in chop: fewer hard hits against the deck frame when waves run up between the tubes.
• Keeps the deck underside drier: less spray reaches the bottom of a plywood deck.
• Shields under-deck components: wiring, fuel lines and steering cables often run under the deck.
• Cleans up the look: the crossmembers are hidden when you view the boat from the water or the trailer.

What it does not do matters as much to a buyer:

• No extra stability: a pontoon’s stability comes from the tubes, their diameter and spacing, not the deck skin.
• No extra buoyancy: the skin is not watertight and adds no flotation.
• Limited impact protection: sheet of 0.025 to 0.050 inch dents easily, and the tubes still take most hits from logs and rocks.

Stability and hull form are covered in our guide to the most stable boat hull designs, which compares multihulls with flat and V-bottoms.

Does Underskinning Help a Pontoon in Rough Water?

Yes, within limits. In chop, underskinning stops waves from hitting the crossmembers, so the boat surges and slams less. It does not raise the deck, add freeboard or keep the bow from burying in a steep wave.

Harris describes the effect as reducing “the surging effects caused by water hitting cross members at speed”. The gain is largest on bigger lakes with wind chop and on boats run fast. A pontoon that idles across a calm cove rarely throws enough water up to notice the difference.

Does Underskinning Stop a Tritoon From Submarining?

No. Submarining is the tube bows driving under a wave, and the deck skin sits above the waterline. Tube diameter, center-tube design, bow shape and load placement keep the bow up.

Sun Tracker pairs the skin with lifting strakes on the pontoon tubes, which add lift at speed. Shifting passengers aft when the bow starts to dig in also helps.

Does Underskinning Make a Pontoon Faster?

It can, mainly at higher speeds. With the crossmembers covered, spray between the tubes no longer drags on the deck frame. Neither Sun Tracker nor Harris publishes a speed gain for the skin alone.

Sun Tracker and Harris both sell the skin inside performance packages built around a third tube. That tells you where it pays off: on boats pushed fast enough to throw water at the deck. For typical pontoon speeds by horsepower, see how fast a pontoon and other boats can go.

Less drag at a given throttle setting usually means less fuel burned, but the saving is small compared with load and engine choice. Our guide to how much fuel a boat uses per hour has a pontoon section with the bigger factors.

Which Pontoon Brands Offer Factory Underskinning?

Several US builders fit underskinning as part of a performance package rather than on every boat. The table shows what each builder’s own material says, with the date checked.

Builder	What it is called	Where it appears	Source, as of
Sun Tracker	Deck underpinning	XP3 performance package (three 26-inch logs, lifting strakes)	Sun Tracker XP3 learning center page and 2021 catalog; checked 2026-10-30
Harris	Partial aluminum skin kit	Sport Package (Level 1)	Harris performance package article; checked 2026-10-30
Harris	Fuller underdeck skin kit	Performance Package Plus (Level 2), all models except the Cruiser	Harris performance package article; checked 2026-10-30
Barletta	Full under-deck skin	2019 L25UC, listed as high-end construction	Boating magazine test of the 2019 L25UC; checked 2026-10-30

Packages and names change between model years, so ask the dealer for the exact coverage on your model and year. For how these builders compare beyond the deck skin, see our ranking of the best pontoon boat brands.

Should You Avoid a Pontoon Without Underskinning?

No. Underskinning is usually an option or part of a performance package, and many owners never need it. It matters most if you run fast, boat on big open water or plan a high-horsepower motor.

Use these questions before you decide:

• Where will you boat? Small calm lakes and rivers rarely justify it, while large lakes with afternoon chop often do.
• How fast will you run? Spray against the crossmembers grows with speed, so towing skiers and tubers favors a skin.
• Is it a two-tube or a tritoon? Performance tritoon packages often include it, so compare like for like.
• Can it be added later? Yes, by a dealer, a metal shop or a capable owner, as long as the crossmembers are sound.

What Material Is Used for Pontoon Underskinning?

Aluminum sheet, normally a marine alloy such as 5052-H32, is the standard material. Owners fitting their own skins report using 0.025 to 0.050 inch sheet, with about 0.032 inch a common choice.

5052 is the same alloy family Sun Tracker uses for its 0.100-inch tubes, and suppliers rate it for good resistance to salt water corrosion. Thinner sheet saves weight but flexes, vibrates and dents more easily. One owner on the Bennington owners’ forum called 0.080 inch overkill for a deck skin.

Stainless steel sheet is not a practical skin: it is heavy and creates a dissimilar-metal joint with the aluminum frame. Wood, including pine, is not used, since it soaks up water and rots under the deck.

How Much Weight Does Underskinning Add?

Very little relative to the boat. Supplier data for 5052-H32 sheet gives the weight per square foot below, and the last column works it out for a 150 sq ft skin.

Sheet thickness (inch)	Weight per sq ft (lb)	Weight of a 150 sq ft skin (lb, calculated)
0.025	0.349	about 52
0.032	0.447	about 67
0.040	0.559	about 84

Weights per sq ft are from Continental Steel’s 5052-H32 listing, checked 2026-10-30; fasteners and overlaps add a few pounds. For context, see our list of average pontoon boat weights with 51 examples.

How Do You Install Underskinning on a Pontoon?

You fasten aluminum panels across the bottom of the crossmembers, front to back, with every joint landing on a crossmember. Each forward panel overlaps the one behind it, and every fastener is isolated to limit corrosion.

The steps below are the general method; follow your builder’s instructions if you are fitting a factory kit.

1. Support the boat safely. Work on a level site with the boat on its trailer or blocked securely, never under a boat held only by a jack.
2. Inspect first. Check crossmembers, brackets and the deck underside for corrosion, cracks or soft wood, and repair them before covering them.
3. Measure the bay. Record the width between the tubes and the spacing of the crossmembers along the boat.
4. Plan the panels. Cut sheets so every edge lands on a crossmember, and mark where wiring, steering and fuel lines need an access panel.
5. Fit from the stern forward. Each forward panel then sits on the water side of the panel behind it, so oncoming water passes over the joint.
6. Fasten into every crossmember. Use stainless self-drilling screws or rivets through pilot holes, with an isolating compound on each fastener.
7. Check after the first run. Look for loose edges, rattles at idle and panels touching the tubes or brackets.

One Bennington owner reports screws about 9 inches apart holding a 0.032-inch skin firmly. A loose forward edge is the usual failure: once water gets behind it at speed, it can tear a panel off.

Should You Fit It Yourself or Hire a Shop?

A careful owner with a drill, sheet-metal shears and a trailer can do it, but most of the work is overhead and slow. A dealer or marine metal shop will cut panels to your crossmember spacing and fit them faster.

Before drilling into the frame of a boat still under warranty, ask the builder or dealer in writing whether it affects coverage. Cost depends on these factors:

• Deck length and the width between the tubes
• Partial or full coverage
• Sheet thickness and alloy
• Factory kit versus shop-cut panels
• Number of access panels needed for wiring and steering
• Local labor rates if a shop fits it

How Do You Prevent Corrosion Under the Skin?

Keep dissimilar metals apart, use copper-free products and rinse after salt water. Stainless fasteners in aluminum can cause galvanic corrosion at the hole if they are not isolated.

Stainless steel does not corrode easily itself, but it is more noble than aluminum. In salt or brackish water, the aluminum around each stainless screw becomes the sacrificial metal. TotalBoat’s guidance for aluminum pontoons covers the main precautions:

• Use aluminum or 300-series stainless fasteners with plastic washers.
• Coat fasteners with an isolating compound such as Tef-Gel or LanoCote.
• Never use copper-based antifouling or primers on aluminum.
• Rinse aluminum surfaces with fresh water after every saltwater trip.

A closed skin also traps salt and silt against the crossmembers, so flush the bay from the sides when you rinse. How anodes protect aluminum is explained in our guide to sacrificial anodes and corrosion protection. If you plan to paint the skin, our guide to painting an aluminum boat covers etching primer and saltwater paint choices.

What Should You Check on a Used Pontoon With Underskinning?

Check the skin itself, then ask what it hides. A full skin covers the crossmembers, brackets, deck fasteners, plywood underside and under-deck wiring that a buyer or surveyor would normally inspect from below.

On a pre-purchase survey of a skinned pontoon, a surveyor typically looks for these signs:

• Dents, creases or torn panels: evidence of grounding or striking debris, which may have loaded the crossmembers too.
• Loose or missing fasteners: rattles at idle and the risk of a panel peeling off at speed.
• White powdery corrosion around fastener heads: a sign of galvanic attack on the aluminum.
• Staining or dampness at panel joints: water trapped above the skin against the deck.
• Soft spots in the deck above: possible rot in a plywood deck that the skin keeps out of sight.

Ask the seller to remove one access panel so the crossmembers and deck underside can be seen. Plywood quality matters here, and our guide to marine plywood grades explains what a sound deck panel should be. The tubes, welds and transom stay visible with or without a skin, so inspect them as usual.

Related Topics

• Do You Need Lifting Strakes on a Pontoon?
• Best Pontoon Boat Brands
• Average Pontoon Boat Weight With 51 Examples

Frequently Asked Questions