prv
Well-Known Member
As far as I understand (always willing to be corrected) any danger lies in the fact that the boat's UK spec. main switch or circuit-breaker will probably only switch off one line/phase/pole and thus for proper protection it needs to be the positive line/phase.
I'm not expert on boating practice with 240v, but ashore a main switch in a consumer unit will always switch both poles. Similarly any other isolators (like the one you're supposed to have before your bathroom fan, although I've never understood what's so special about that particular appliance) must isolate both poles. If you have a simple switch (like a lightswitch) in the live conductor only, then it's not an isolator and should not be relied on if you're going to work on parts that are normally live.
Pete