GUMPY

Are you saying a boat connected to mains on its own cannot suffer from galvanic corrosion? Think again! No need for another boat to be nearby. https://www.victronenergy.com/media/pg/The_Wiring_Unlimited_book/en/galvanic-corrosion.html Galvanic corrosion is caused by an electric current that enters a boat via the shore power earth wire and returns back to shore via the water. These currents can cause corrosion to the boat’s underwater metals, like the hull, propeller, shaft and so on. This current is called galvanic current. Galvanic current is a DC current. It is caused by the natural voltage difference between metals. A galvanic current can only exist when there is a closed electric circuit. A conductor belonging to another electric circuit can be part of the galvanic corrosion circuit. If a boat with a metal hull is near the shore a natural voltage difference of 0.1 - 1 Vdc exists between the hull and the water. This potential difference leads to nothing as long there is no completion of the electric circuit. But, as soon as shore power is connected to the boat, the shore earth is automatically connected to the boat's hull and the electric circuit is complete. Now the following circuit is made: hull - water - shore - earth spike - earth wire - hull. A galvanic current will flow through this circuit. The galvanic current partly runs through the AC circuit but is not related to that circuit. Current will continue to flow until the potential difference is eliminated. The height of the current depends on the resistance of the electric circuit. The resistance is determined by factors like the length of the shore power cable and local earth spreading resistance.

Not correct in my book. With an earth stake and NE bonded it's just the same as being connecting to the mains. It only needs some metal bankside in the water doesn't even need to be rubbing against it. Or are all the boats with IT and GI fitted doing it for no reason?

Unless an Isolating Transformer or GI is fitted that's a sure way of inducing galvanic corrosion.

Were the holes filled or just a patch over them? If the latter then an angle grinder will remove the patch with ease.

Plasma cutter!

I think it was an over zealous surveyor pushing his own agenda. Only on Idleness has it ever been mentioned and that was when it was mandatory for the BSS sometime in the late 1990s. Loddon has similar vents and it's never been mentioned.

I suspect the 10" comes from an old boat safety scheme rule about hull exits. Mine at the time were all only 2" above the water line but the internal height was 10" so it passed. If the rule hasn't been dropped completely it now is only relevant to hire boats.

Scary thing is my solar battery at home is 350V/17kWh The solar arrays are 120v/2.2kW. Strangely there are more warning notices about AC than DC.

No it was you that said there was no RCD to protect the user. I was merely being sarcastic as usual. BTW nothing electrical is dangerous provided you follow the correct procedure and if you have to ask you probably won't follow the correct procedure

That's not the area being discussed. Yes that did happen, more than once but only after a period of exceptional rain.

I can't remember a time in the last 40 years that the GU became unnavigable because of flow. Ice yes but not flow. It's not something I ever considered when I kept the boat on the GU.

Tell me how the RCD might work. As for DC voltages I used to build DC PSUs that were only half an amp but at 2500volts. That will kill you instantly if you get it wrong. They would still be live for 24hrs after switch off even with a bleed resistor across the caps. I once brushed past an open CType that I used for the DC connection, the DC tracked across the back of my hand and burnt a hole. The wife heard the bang 100ft away down the garden.

I used to put a blanket or two over my panels to shut them down even in bright sunlight. I could then pull the mc4 with no sparks.

One of THESE should do nicely Second hand but cheap enough. I used one for years on the boat with a Huawei router.