Hello, 

My understanding: 

sv Viva #374 is wired for Europe 240V with 3 prongs; Phase (hot), Neutral, Ground

Ala Wai Marina in Hawaii does have 240V with 3 prongs, 2 Phases (hot)  and  Neutral. No ground, plug protected by a breaker at the Marina socket..
110V is coming between one phase and neutral. Then 240V is coming from the 2 phases.

I bought a socket NEMA L6-30P wich is fitting the Marina socket.   

My questions are:
 
1-How do I wire this NEMA L6-30P socket to replace the European Socket?

I foresee 2 mutually exclusive options: 
11- wire one US phase in the European Neutral
12-combine the 2 US phases in the European Phase 
Both options seems wrong ... 

2-Do I have to install a 30A "galvanic isolator" - as I have seen in previous threads - if the Marina socket is protected by a breaker?  

Any advice and tip will be greatly appreciated.
Thanks 
Dominique Guenot
+1 917 826 0945
sv Viva #374