That's a nice idea but an absolutely shocking design and execution.
The mounting bracket just makes you wince with its sharp corners, only being fixed at an edge and then sticking out the way it does!! And that's before the exposed electrical in a maritime environment.
Why not use a right angle bracket so that the mounting board is flat to the side of the tank? Why have those sharp edges on the board? Why not encase the motor with an old Tupperware box screwed down onto the board and sealed with a bit of silicone?
But maybe the biggest question is how is this chap permitted out without his carer?
If you have a marine fuel tank, a boat and a desire to electrically pump fluid why wouldn't you just put a marine pump in via the filler and bring the power through the breather hole? I think the chap has a screw lose.