Baseboard electric heaters can be run on DC as well as AC power. You don’t lose the inefficiency of putting it through the inverter and you don’t need as large of an inverter.
Convert to AC near your panels … then run it to your load. Keep it simple … power consumption in transformers would negate any gain doing step up and down transformers. Running heavy gauge dc wire to near the load b4 inverting is un economic and just stupidity.
Sounds like I have the same bow thruster… soon I will be replacing my pb- acid batteries with lithium too. I’m tied in to my house batteries with one battery within three feet of the bow thruster motor… this takes care of ir drop. Just an idea for you.
Put two cells in parallel then take 16 of these two cell groups and hook it up to your BMS or if you need to charge/ discharge at 200 amp build two 16s batteries with two BMS