After the incident with water in the electronics I decided to waterproof the electronics so that it would less likely get damaged. My solution is to put balloons on the most critical electronics. This means the Arduino and the ESCs. I have secured the balloons with strips. The receiver is already splash proof and filled with Silicone.
At the ends of the balloons with the wire exits I intend to add some Vaseline to seal the small holes there might be around the wires.
One concern is how long balloons will last before dissolving? It might be hard to get to the balloons for replacement.
Furthermore I re-wrote the control program for the Arduino so now I am in possession of Timer1 instead of letting the servo library own it. This means that the program should be running more precise and better calculations should be made. It will however be some time before I will know, as I'll have to replace the Arduino in the boat before I can re-program it.
I also put some effort into placing the receiver antennas as recommended in the receiver guide, meaning one antenna is placed horizontal and the other antenna vertical.
I intend to take this boat out tomorrow and try if the antenna positions are better?
Here are some pictures of the secured electronics and the carefully placed antennas: