Mains 240v conundrum

[Crazy-Diamond]

I have a simple mains distribution panel in my boat. The breaker switches have decided not to remain in the “on” position even when nothing is connected to them. Which I don’t understand. It has been working fine.
Also, I get 240v when I measure from the earth bussbar to the neutral bussbar, which seems most odd. Surely there should be no voltage on the earth at all?
If there is a fault somewhere with a mains appliance it could be sending volts down the earth. I have a galvanic isolator which is not showing a fault. But with nothing connected where are these volts coming from on the earth?

 

[Boater Sam]

Sounds very dangerous.
Has the GI gone O/C?
Tripping the RCD?

Is the polarity reversed and it is really the neutral that is now the live?

 

[VicS]

I have a simple mains distribution panel in my boat. The breaker switches have decided not to remain in the “on” position even when nothing is connected to them. Which I don’t understand. It has been working fine.
Also, I get 240v when I measure from the earth bussbar to the neutral bussbar, which seems most odd. Surely there should be no voltage on the earth at all?
If there is a fault somewhere with a mains appliance it could be sending volts down the earth. I have a galvanic isolator which is not showing a fault. But with nothing connected where are these volts coming from on the earth?

240 volts between the earth and the neutral suggests that either line and neutral are reversed or line and earth are reversed.
The latter will create a very dangerous situation and with that possibility in mind you should not attempt to reconnect the shorepower supply until the cause has been identified.

If the gi is open circuit, or the earth itself disconnected, a very small line to earth fault or maybe a reverse polarity indicator could give a 240 volt earth to neutral reading on a digital voltmeter.

When you say "breaker switches" exactly what do you mean?
Are they mcbs, ie just overcurrent breakers, rcds or rcbos?

It sounds like a job for a properly qualified electrician before you electrocute yourself.