Your boat looks cool but it will be hot in the sun, will that sun heat warp it?
I have repaired small plastic parts using a soldering iron.
I repaired some gouges and cracks on my plastic black HDPE Ram truck bedliner. At first I tried soldering and adding more plastic using a black HDPE oil jug cut into strips.
But was messy and hard to make it look good. I also tried a heat gun, but it is too broad application of heat, meaning you could deform or melt too large an area of plastic.
But I found if I use a propane torch and hold the plastic strip in the torch, they melt and drip onto the bedliner and it is so hot it instantly fuses to the plastic. You have to sometimes blow out a burning flame. It really worked well using the torch and drip method. You can also prime the plastic to be dripped on with a quick swipe of the torch.
Using the drip method, you can easily build up thick layers of plastic. It sort of looks like melted candle wax. Keep a hose nearby in case you screw up. But it is not hard to drip plastic onto HDPE to get a good bond. Advantage is the whole piece does not get so hot in that area to deform and melt.
