Norm-
From what I'm able to discern your
150 hp Suzuki has a single 44 amp alternator output.
The new
Suzuki 300 and the
250/225/200's have a 54 amp output.
The only one that is mentioned to have a dual output is the 300:
"Suzuki engineers know how important a full arsenal of sophisticated
electronics is to today’s modern fisherman, so they’ve included a powerful
12V 54 Amp alternator that delivers plenty of juice to power up fishfinders,
GPS chart plotters, radar systems, baitwell pumps, spreader lights and
more. The DF300 also features a dual circuit charging system that can
be adapted to accommodate the dual-battery configurations often used on
large boats. The system is designed to charge both the cranking and
house batteries simultaneously but on independent circuits. Boaters can
drain their house battery running trolling motors, electronics or pumps and
still have a fully charged cranking battery for starting the outboard motor."
SOURCE
And Specifications.
That Xantex XC5012 Multi-Stage charger requires 120 VAC to run it's three battery circuit outputs, and your options are to
1) run it on Shore Power, or
2) generate 120 vac with the inverter, then use that 120 vac to run the charger, and charge the batteries. At least it seems so at first.
But, with this second choice, we're stuck in a loop! We're using the battieries to charge themselves!
Current comes out of the batteries to power the inverter which then generates the 120 volt current to power the charger which returns current to the batteries. Either we have a perpetual motion machine, or something's not right.
We could add in the current to the batteries to our system from the motor's alternator, but why not just charge them directly with current from the engine's alternator, using the appropriate manual or electronic switching units/relays to prioritize the charging?
Another, somewhat less serious problem, is that if the charger is going to put out it's full 50 amps, a 44 amp alternator won't supply the inverter with enough power at 12vdc to convert to 120 vac then back to 50 amps 12vdc in the charger. (Heat loss inefficiency, etc.)
So your 1800 Watt inverter is a good idea (with enough battery capacity to supply it), and the 50 amp charger is also a good choice, but only to use on Shore Power. Connect the engine's single alternator to the batteries through the appropriate switching gear, and you'll be all set to go.
Sell the Guest 5/5/10 or find another use for it on another boat, if you have one.
When you do all of this, check out all your batteries to be sure they're in very good condition, especially if you'll be connecting them in parallel at any time with the switching gear that distributes the alternator's charging to them, or have them simply connected in parallel to supply power, because if one is weaker than the others, it will draw them down to it's level.
Hope this helps and it correct, it's late and I'm not as sharp as I am during the day as it's now after midnight on Sunday 12 am!
Good Luck!
Joe. :teeth :thup