Thanks for the quick responses.
Ummm..... denise and scotty, please dont do any electrical work your self on your boat as 240V is NOT 2 x 110V.
And yes we do have neutral.
I think the do nothing approach appeals most
in the US 240 is two legs of 110/120. the 2 phases are 180 degrees out of rotation to each other. if you open my electric panel or any house panel in the US you will find 2 hot legs. if you read between the legs its 240, if you go from either leg to neutral or ground its 110/120.
as i said i did not think you had a neutral like we do, ie neutral and ground are bonded or connected in the panel. it looks like i am wrong from what you said, if you measure from the hot to the ground do you get 240v? i kind of thought europe used 2 legs, with neither being a ground/neutral like we have. i could be wrong i have never worked on electric in europe or even been there.
the reason the US has set up our power like this, is one we have had it this way for a long time. the other reason is for normal things like lights, tv's, microwaves etc using 110v is safer from the shock point of view ie less likely to get killed. now running higher amperage to get the same wattage is more likely to burn a house down. we started with 110 v, then as things like electric dryers that needed more juice came around it was easier to install the 120/240 v system like we have with out throwing everything 110 volt away. it was easy to install a transformer out on the pole that had a second tap 180 degrees out in the freq to get the 240 and then run another hot leg inside.
the funny one is commercial electric is 3 phase 277/480 where the are 3 phases at 277 to ground. then we use a transformer to step it down to 120/208 with 3 hot legs in the panel. now not all places have the 277/480 coming in some go straight for the 120/208
btw i am a master electrician here
edit 83xt4 here is a wiki answer web site you might get a kick out of