look on the southern airboat forum lots of products they use you repairing/protecting the poly on the bottom of the airboats, plus it will help paddling through grass/weeds
Partite 7310, This two-part methacrylate adhesive is used for filling and sealing scratches and gouges in three layer polyethylene and Oltonar/Royalex€ canoes and kayaks. Combined at a 1:1 ratio, it has a working time of 15-18 minutes and fixture time of 30-35 minutes at room temperature. 731MMA offers a combination of high strength and stiffness as well as the ability to bond a wide range of materials.
When I bought mine, the previous owner had worn a hole about slap through the hull at the keel. I bought a plastic welding rod from harbor freight and used cut pieces from a plastic bucket to fix it. Like the the post above me said, you could use a heat gun, too. Plenty of videos on YouTube.
Don't use epoxy....Use a plastic welder and it will be stronger than factory (if you use the screen) and will flex as the boat should. we weld boats weekly and have never had an issue with the welds....you must use the same type plastic for best results...your kayak or canoe manufacturer usually can supply welding sticks of the exact color and plastic...you can but a cheap welder on amazon- https://www.amazon.com/Chicago-Electric-Welding-Systems-Plastic/dp/B006ZBCCKO for about $30....do it right....you wont regret it.
If it's polyethylene, plastic welding is the way to go--you can use any other piece of PE plastic as stock. If you have large thru-holes, put a piece of duct tape on inside to support the welding.
There's nothing readily available or affordable that 'glues' polyethylene--fortunately the plastic welding is relatively easy.
put some UHMW on the bottom and you won't ever have to worry about it again. You can slide it down the asphalt to the ramp or launch and it will be slicker than a baby's hind end.