What DC powered A/C are you contemplating using?
I'd be interested to hear how practical it is given the power requirements.
The DC Breeze by Glacier Bay is a small unit (5000BTU) and likely too small for your boat and it requires 48 amp hrs to run. With a 400 amp bank and no other load, this would theoretically equate to a run time of 5 hours maximum.
However, for a 43 ft boat, you are going to find your need is more like 16,000 BTU if not more or 3 times the A/C load and at least 3 times the power requirement. This ignores inherent loss and inefficiency of the electrical system. The battery capacity required becomes the limiting factor.
As you increase battery capacity, you also increase charging requirements, larger alternator, solar power, genset capacity, etc. making the total system cost equal to or exceed that of the typical AC powered air conditioner.
Running a typical AC powered air conditioner off an inverter is impractical for a number of reasons including those mentioned above as well as the consequential additional inefficiency from inverter conversion loss and additional power demand above that previously stated.
Example:
my 16k BTU A/C which barely keeps my 40 ft boat cool in New England heat requires 14 amps at 110V or 150 amp hrs at 12 VDC. With my 440 amp hr battery bank, I could run it theoretically, with no other loads, for a bit over 1 hour before necessarily recharging the batteries and that assumes lots of things including a heavy duty cycle 3000+ W inverter capable of handling the load for a sustained period.
