The ladders are in a different, higher-angled position on the side of the van in the later images of the completed "riverboat" than they are in the beginning images, when the ladders are more horizontal.
In the finished "riverboat", the paddle-wheel just "skims" the surface of the water; it is not lowered far enough into the water to be able to push the "riverboat" along much at all, even if it had baffles still in it for the water to be pushed against with.
The diagonal marked lines for where the van's driver's door is later going to be cut to allow the door's window-frame to clear the ladder are clearly visible in the beginning of the segment, long before the ladders have been raised up that far.
The ladders are visibly duct-taped to the sides of the van in the initial views where the ladders are more horizontal, but then in the later shots where the ladders are at a much higher angle and the paddle-wheel is attached, there is almost no duct tape visible anywhere on the side of the van, with none of the tape swathed over the ladders as if it is holding them on, revealing that the ladders are in reality welded or bolted in place, not taped on.
The "paddlewheel" on the "riverboat" starts to turn long before the drive-belt and rear wheel move, obviously showing that there is a separate drive-mechanism turning the paddles, and that the paddlewheel is turning the van's drive-wheel, not the other way around.
Red tells his viewers to record the fax-machine sound to fool telemarketers, but he hangs up the phone before he's recorded all of the "fax-squeal" sequence.