Last updated: August 20, 2026
Jon boats are the boats most likely to be left uncovered, and the reasons are understandable. The hull is aluminum, there is no upholstery worth protecting on a bare model, and a cheap tarp seems like a reasonable answer to rain. Then a season of standing water, leaves and pooled debris does its work on the floor, the wiring and any seat that is bolted in.
This guide covers what a jon boat cover actually has to do, why a flat, low-sided hull is harder to cover than it looks, and how the cheap fixes compare to a purpose-built cover. Universal fit is the realistic option here, and getting a universal cover to fit well is mostly about measuring and about what holds it down.
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Quick Answer
What kind of cover does a jon boat need?
- A universal fit jon boat cover sized by centerline length and maximum beam, not by the boat’s nominal feet.
- Something to shed water in the middle. A flat hull gives a cover nothing to drape over, so a support pole is part of the purchase.
- A real tie down system, because low sides mean wind gets underneath easily.
- Vents or a deliberate airflow gap, so the space under the cover does not turn into a mildew farm.
Bottom line: measure centerline length and beam, buy the cover for those numbers, and budget for a support pole and straps.
Why a Jon Boat Is Awkward to Cover
Most boat covers rely on the shape of the boat to shed water. A windshield, a console, a raised bow or a gunwale that rises toward the front all give the fabric somewhere to run off. A jon boat has none of that. It is a flat, low, open rectangle, so a cover laid over it forms a shallow basin instead of a roof.
Water then collects in the middle, and a pool of rainwater is heavy enough to stretch the fabric, pull the hems, and eventually find its way through the seams. In freezing conditions the same pool becomes ice, which is worse.
Low Sides and Wind
The second problem is wind. With almost no freeboard, there is little for a cover to grip, so a gust that would pass over a bowrider gets under a jon boat cover and lifts it. Covers that come off in a storm usually fail at the tie downs rather than in the fabric.
Universal Fit, Honestly Framed
A custom cover made for your exact hull will fit better and last longer than any universal cover, because the pattern follows the actual sheer line and the fabric is not fighting the shape. It also costs a multiple of the universal option, which is why most jon boat owners are not buying one.
The realistic goal is a well chosen universal cover rather than a poor imitation of a custom one. Universal covers are sized by ranges, and getting one that suits your hull closely, then adding support and proper straps, gets you most of the protection for a fraction of the outlay.
How Universal Covers Are Sized
Universal jon boat covers are listed by a centerline length range and a maximum beam. iCOVER, for example, lists both figures on each of its jon boat cover sizes, so a cover is described as fitting boats up to a stated length with a beam width up to a stated maximum. Both numbers have to work, not just the length.
Measuring Your Boat Correctly
Measure the centerline length from the tip of the bow to the top of the transom, following the deck rather than the ground, and measure the beam at the widest point across the gunwales. Write both down before you shop, because a hull sold as a given number of feet is often longer or shorter in reality.
Anything mounted on the boat changes the measurement. A bow-mounted trolling motor, a raised casting deck, a center console or tall pedestal seats all add to what the cover has to clear, and a cover sized for the bare hull will stretch or refuse to close over them.
The Overhang Trap
Buying a size up to be safe creates its own problem. A cover that is too large flaps in wind, holds more standing water, and rubs against the hull as it moves. Aim for the size range your measurements sit inside comfortably rather than the next one up.
Covers and Support by Situation
Smaller Jon Boats for Storage and Light Towing
For a typical small jon boat kept on a trailer at home, a waterproof universal cover in the correct length and beam range covers most of the need. Look for a hem that will actually take tension, reinforced corners, and either a drawcord or webbing loops around the perimeter.
Larger Hulls and Highway Towing
Longer jon boats and anyone who tows regularly need a heavier fabric and a cover rated for trailering. Highway speed is a far harder test than a storm in the driveway, and a cover not built for it will flog itself apart at the seams within a few trips.
The Part That Stops Water Pooling
An adjustable support pole stands in the middle of the boat and lifts the cover into a peak so rain runs off. On a flat hull this is not an accessory, it is the difference between a cover that works and a cover that fills with water. Poles with a padded top cap protect the fabric from wearing through at the contact point.
Holding It Down in Wind
Straps that pass under the hull and cinch tight are what keeps a cover on a low-sided boat. Kits with quick release buckles make removal quick enough that you will actually put the cover back on, which matters more than any fabric spec.
Cover Options Compared
| Option | Sheds water | Tow rated | Best suited to |
|---|---|---|---|
| Poly tarp and rope | Only with a pole and effort | No | A short term stopgap, nothing more |
| Universal jon boat cover | Yes, with a support pole | Many models are | Most owners, storage and towing |
| Cover plus support pole | Yes, reliably | Depends on the cover | Outdoor storage through wet seasons |
| Custom fit cover | Yes, best of the group | Usually | Owners keeping the boat many years |
Airflow and Mildew
A sealed cover over a damp aluminum boat traps moisture, and trapped moisture in warm weather grows mildew on everything soft inside. The fix is airflow: vents built into the cover, or a deliberate gap at the transom corners, so air can move through rather than sitting still.
Owners storing a boat over a long wet season often add a moisture absorber inside as well. Neither vents nor absorbers help if the boat goes under the cover wet, so pull the plug, let the hull drain and dry, and get the cushions and life jackets out before the cover goes on.
Store the Bow High
Leaving the trailer jack raised so the bow sits higher than the transom lets any water that does get in run to the back and out through the open drain. It costs nothing and prevents the standing puddle that quietly ruins a floor.
Common Mistakes When Buying a Jon Boat Cover
Buying by the boat’s advertised length alone is the standard error, because the beam is what actually decides whether the cover closes. The second is skipping the support pole and then blaming the cover when it pools and leaks.
Third, and most expensive over time, is using a hardware store tarp as a permanent solution. Tarps do not breathe, chafe against the gunwale until they shred, and hold water against the hull rather than shedding it. As a cover for one wet weekend they are fine. As a season-long answer they cost more than they save.
Frequently Asked Questions
What size cover do I need for my jon boat? One sized for your measured centerline length and your maximum beam. Universal covers such as iCOVER’s jon boat range list both a length and a beam limit, and your boat has to fit inside both figures rather than just the length.
Can I just use a tarp on a jon boat? For a weekend, yes. Long term a tarp traps moisture, chafes the gunwale and pools water, so it tends to cost more in damage than a proper cover saves in purchase price.
Do I need a support pole under a jon boat cover? On a flat hull, effectively yes. Without one the cover sits low in the middle and collects rain, which stretches the fabric and eventually leaks through the seams.
Will a universal cover fit as well as a custom one? No, and it is worth being clear about that. A custom cover follows your hull’s exact shape and lasts longer. A well sized universal cover with a support pole and proper straps gets you most of the protection for far less money.
Can I tow with a jon boat cover on? Only if the cover is rated for trailering and is strapped down properly. Highway airflow is much harder on a cover than weather is, and a mooring-only cover will tear.
How do I stop mildew under the cover? Dry the boat before covering it, remove cushions and life jackets, allow airflow through vents or a deliberate gap, and store the bow higher than the transom with the drain plug out.
The Bottom Line
A jon boat cover is a measuring job first: centerline length and maximum beam, taken with everything that is actually mounted on the boat. Add a support pole so the flat hull can shed water, strap it down properly because low sides invite wind, and let air move through so the space underneath stays dry. For the wider cover decision our boat cover guide compares fabrics and fit, and our tarp versus cover comparison puts real numbers of seasons behind the cheap option.