In the picture above the scraper blade fell in such a way as it connected the AC neutral to the AC ground. The boat was tripping the GFI Receptacle at the dock and that started the search to find out why.
Any connection between AC neutral and ground on board is very dangerous because it makes the water a parallel path for current back to ground and potentially could electrocute anyone in the water around the boat.
Be aware that some domestic stoves have a built in connection between neutral and ground. If present it has to be removed before the stove can be used on a boat