How to Under-Skin a Pontoon Boat (and What You’ll Need)

how to under-skin a pontoon boat

The possibilities are limitless when it comes to customizing and modifying your pontoon boat. And although a lot of the changes you might try involve aesthetics and amenities, there are others that might deserve the same time and attention. Under-skinning for instance, might not be readily apparent, but it does serve a reasonable purpose.

Under-skinning was once recognized for its ability to help improve a pontoon boat’s speed. But these days, boat owners have found that it does a whole lot more than just that. Find out how to under-skin a pontoon boat and why you might want to consider doing it with this quick guide.

What is Under-Skinning and What is It For?

Under-skinning involves covering the underside of your boat with a sheet of aluminum, among other viable materials. This creates a smooth surface as opposed to the often irregular appearance that comes as a result of the cross-members that stretch between your tubes.

Back in the day, under-skinning was though to significantly improve a pontoon boat’s speed. But recent studies have found that the modification might add no more than 1-2 miles per hour to your top speed. However combined with other speed enhancing adjustments, underskinning may possibly produce more significant results.

While its speed benefits might not be too out-of-this-world, under-skinning also offers a bunch of other advantages that could make it a worthy addition to your boat. These include:

  • Protecting your boat's underside from water damage and dirt
  • Deflecting minor debris and other small objects that could cause damage
  • Lessening water sprays for a smoother ride
  • Improving the appearance of your underside (not that it really matters)

Plus, under-skinning is a pretty cheap job that you could do yourself over a weekend. So given that it can provide some pretty helpful advantages at such a low cost, it’s no surprise why so many pontoon boat owners have found it to be a worthy modification.

What You’ll Need

If you’re convinced that under-skinning is the right thing for you, then you’re going to need some supplies. These are some pretty common tools and materials, so you shouldn’t have too much trouble finding what you need. These include:

An Aluminum Sheet

aluminum sheet

Marine-grade aluminum proves to be the best material for the procedure. Not only is it impressively durable, but it’s also lightweight so you won’t have to worry about the sheet weighing down your boat. They’re available in a number of thicknesses, but a sheet at just 0.065” should be just right.

Check out the RMP 6061-T651 Aluminum Sheet.



You’d think that any nails or screws would do, but not quite. As any experienced boat owner knows, sticking together aluminum and low carbon metals will cause unpleasant electro-chemical reactions that could reduce the lifespan of your under-skinning project. Instead, go for stainless steel fasteners to secure the sheet against your cross beams. Don’t forget to get a set of rubber marine-grade washers to boot.

We recommend using Stainless Steel Tek Screws or get yourself the Sutemribor Nylon Flat Washer Assortment Set.

Power Drill

power drill

Of course, you’re going to need a handheld drill to push those fasteners in place. It should also come in handy for punching holes into the aluminum sheet so you can anticipate the placement of your fasteners.

Aside from all of that, you’re going to need the other basics like a pencil or marker, measuring tape, and maybe a pair of protective eye wear. You might also want to wear some work clothes since you’re going to be working underneath your boat.

We like the Dewalt Cordless Drill/ Driver Set.

How to Under-Skin a Pontoon Boat

Now that you’ve got everything you need, it’s time to get to work. Follow these steps to properly and safely under-skin your pontoon boat as efficiently as possible:

Measure Out the Sheet

When under-skinning a pontoon boat, you have one of two options. The first is to attach the aluminum sheet as one piece. The other is to cut it up into several panels before attaching them to the bottom of your boat.

The benefit of working with a single sheet of course is that you get a solid barrier against water and debris. It also turns out to be much smoother, which may marginally improve pontoon boat performance by streamlining the underside even further.

Then again, there are downsides. Working with one massive sheet can make the task doubly difficult. Unless you have an extra set of hands at the ready to help you with the installation, then you might find yourself wrestling with that sheet throughout the process.

On the other hand, you could always cut it up into lots of smaller pieces. This can be helpful in that it lets you work with smaller panels that are significantly easier to handle even if you’re on your own.

The drawback with this though is that you end up creating a bunch of seams that could allow water to penetrate the under-skin. This also turns out to be the cover’s weak spot where you might anticipate damage to start. And then of course there’s the fact that multiple pieces also reduces the streamlined effect that you might be going for.

Once you decide to go with a full sheet or a bunch of smaller ones, then you can measure the width of the sheet. As a general rule, you’re going to want to leave at least 0.5 inches of allowance on either side of the under-skin. This provides a way out for water, ensuring that moisture doesn’t stay stagnant between the under-skin and your boat’s underside.

Fasten Them in Place

Fastening the sheet in place is about as simple as drilling holes and securing the aluminum with your stainless steel fasteners. You can also use a center punch with self-tapping screws.

If you’ve chosen to go with a bunch of smaller sheets to make the installation easier, don’t forget to allow at least a 2 inch overlap at the seams. It’s also important to make sure that you position the seams right over the cross beams so there’s something underneath to secure against.

An Afternoon’s Work

When you find out how to under-skin a pontoon boat, you’ll see that it’s something you shouldn’t really have to pay a professional for. Simple, easy, and pretty straightforward, under-skinning is a cost effective way to improve performance and protect your boat - after just a weekend’s worth of moderate DIY work.

Scroll to Top