I'm going to go way back to the original question.
-- I'm assuming that you won't have any 240v equipment
on the boat
-- and the air conditioning
will be not more than about 20,000 BTU
The only time you'll really need the 50amp service
is with the air conditioning
as air conditioning compressors briefly draw high amperage on startup that can easily pop 30amp dock
My first choice is to install a 50amp 120v outlet on the boat (with appropriate breakers etc inside). I'd then buy a 50ft 30amp cord and 50ft 50amp 120v cord with adapters such that you could plug
into 50amp/240v or 30amp 120v at the marina. You can also connect the two cords together to get 100ft of 30amp in case the power pedestal
is way in the wrong place. This is very simple wiring
in the boat but does cost a little more in cords and adapters. You end up with a lot of flexibility for your money
. Most of the time you don't need air conditioning so you would just use the 30 amp cord (and pay for 30amp from the marina).
The alternative would be two 30amp boat outlets but this would still put the air conditioning on one 30amp outlet. You have to be sure that the air conditioner starting load would not exceed this number. It's also more complicated to wire safely inside the boat. My bet is that it would cost more in the end than the single
I have a version of the first solution and it has served me well.