50 amp boat, 30 amp shore power

That may work for some boats, but mine has an isolation transformer on the input that needs to 'see' 240/250 volts. So if I can't find two outlets on opposite phases, I am out of luck and have to run the genny. The transformer also has an automatic boost function, so if the input is a little low, it will step up the voltage by about 15%.

There are always exceptions. I understand the need for voltage boost, but why woud they need an isolation transformer for the entire system? That has to be one expensive transformer!
 
There are always exceptions. I understand the need for voltage boost, but why woud they need an isolation transformer for the entire system? That has to be one expensive transformer!

Having the isolation transformer gives an additional layer of safety as well as preventing galvanic corrosion due to stray currents, say a 'leaky' boat or a shore cord in the water. It's about a $3000 transformer.

http://www.charlesindustries.com/main/ma_iso_bost.html
 
Some help to understand single phase vs. three phase (two phase is rarely used):
 

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Just so its clear to everyone, you can also have three phase 208, which is where the 15% boost I mentioned earlier really comes in handy.
 
Very confusing since Y will give you 208 volts and delta will give you 240 volts. It is all based on the transformer configuration. 99% of the marinas will have 240 volt delta configurations otherwise boats that require 240 volts will not operate properly. This all stems from how a transformer is tapped and blah, blah, blah.
It is very confusing because when Ken says a Y or delta he is talking about the internal wiring of a transformer (Because he is a electrician) and when most of the people on this forum talk about a Y they are talking about a adapter cable shaped like the letter Y. These adapter cables come in several flavors
30A to 2 30A's Used from a single 30A dock connection to the 2 30A connections Warning this adapter does not supply the boat with the 60A it really wants to run everything
240V 50A to 2 30A's This provides 2 120V circuits out of phase to the 2 120V sides of the panel but only 50A of the 60A
and the one this thread is about
2 30A's to a 50A. This enables you to connect to 2 30A dock outlets to 240V 50A boat. It only works as many on this thread have said if the dock outlets are different phases.

Bruce
 
...
240V 50A to 2 30A's This provides 2 120V circuits out of phase to the 2 120V sides of the panel but only 50A of the 60A...
Bruce

Actually the 240V/50A outlet on the power pedestal is 50 amps per leg, or 100A of 120V total. So there is plenty of power for 2 30A circuits.
 

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