Not sure what kind of cranking amps a 150 hp outboard draws but you might want to confirm that the cranking amp requirements match the capacity of your proposed lithium batteries. Does that "old bass boat" start up in under 3 seconds or it a 15 second starter?
You would hate to "suck the guts" out of your lithium golf cart batteries by using them as starter batteries ... I am not sure if they are really designed for that.
You might want to consider using a single $100 lead acid "starter" battery for your outboard and use the expensive 4 lithium battery set up for both the accessories and 24 volt trolling motor. That might be a safer combination.
Good idea to use a shared lithium pack for both your cart and boat
