As noted, I am a fan of combining the battery banks so as to have one large bank as opposed to the oem two separate banks. BUT there is one caveat:
It is theoretically POSSIBLE to drain the banks so that you can't start a main. I say theoretical because in the 5+ years we have had the Outback that has never happened and hasn't even come close to happening. In one case, the boat was on the hard for 72 hours with the outback powering the fridge. When put back in the water the engines cranked/started instantly with no hesitation at all. However, because it is possible, I would recommend that if your genny is the original or a replacement that uses a 32v starter motor, you leave the banks separate as per oem. Yes, charging both banks might be an issue. But more later on that.
If you have newer genny with a 12v starter and the associated 12v batt(s) to start it, then the possibility of not being able to start a main becomes not much of an issue because you can always start the genny and charge the main batts. Again, this has never been an issue for us and we anchor out; we virtually never stay at marinas. The main batts/inverter easily supply the load needed overnight and have yet to be less than 80% charged in the morning. That includes running the usual stuff - Fridge, sat TV, hair dryer, coffee maker, microwave, stereo, whatever.
If you choose to combine the banks, I recommend a battery switch so you can combine/decombine if you wish. I have never decombined them but I think it's a good idea to be able to. If you decombine, then you are back to the oem setup EXCEPT, as I mentioned earlier, the Outback will only be charging one bank (set it up to charge the oem house bank when decombined). But that's not a big deal in the operational scheme of things while cruising since the start bank will have no load on it. All it has to do is start the engines and, with no outgoing load with the engines off, there is nothing to deplete the batts. Then, just like your car, after starting the engines the alternators recharge the batts for the start bank. Back at the marina and on shore power, combine the banks for extended absences so the Outback will keep all batts in good condition.
I have yet to find the slightest down-side operationally to combining the banks and, per Calder, one large bank is more efficient than the two smaller banks. But again, I realize that some folks are not comfortable with the idea that you could possibly deplete the main batts and be left without the ability to start them.
Another issue with the outback is whether to utilize the "pass through" circuitry or not. I think it's great; others prefer not to use it. One possible downside with using the pass-through is that it is limited to 30A @ 120VAC. That 30A is the total that can be utilized, including battery charging. What that means is that if, for example, you are running 15 amps of normal household loads - whatever they might be - AND the charger wants to apply a full charge load to the batts, the maximum that can be applied to the charger will be 15A. THe charger output is reduced as necessary based on other loads. So if you were pulling 25A of other loads, the charger could only get 5A. (The most the charger will use by default is 19A.)
In reality, this has never been an issue. Remember, we are talking Amps at 120vac. The charging amps delivered to the 32v batts is much higher than the original Ferro charger could deliver and, in fact, the Outback can recharge the batts in 1/3 the time that our old Ferro charger could with the batts at the same discharge level.
One more item to be aware of re the pass through - you could set it up to provide power to all 120vac loads. But now the 30A pass thru could easily be a problem, especially at the dock. 30A is not much when you consider everything that could possibly be on at the same time. So a better way is to select particular circuits and have the inverter/pass-thru provide power to them ONLY. In our boat, I selected the circuits that power: the fridge, the microwave and coffeemaker the davit, the upper starboard salon plugs (TV, stereo, etc) the Cablemaster, and one outlet in the master stateroom (tv, hairdryer if needed). It's easy to split the circuits out in the elec panel BUT it does require setting up a separate ground buss for the circuits supplied by the inverter and isolating the existing breakers for the particular circuits so they are powered by the inverter, NOT by the normal hot buss in the panel. It's NOT difficult at all, though it may sound that way.
All the parameters of the Outback are remotely adjustable with the addition of the "Mate" remote unit. Be sure to purchase that option. If you don't, you will regret it later. I went without it for a year and it was stupid. The mate allows you to use all the capabilities of the inverter and to change literally every setting imaginable to fit your specific needs.
