On a lot of newer boats I've seen, they have gone to a smaller pure starting battery and a larger single house battery - with a battery isolator in place so that:
-both batteries charge when engine is running
-you never mess with your battery switch (unless you for some reason need to start with the house battery)
-your starter battery never gets discharged cause you fell asleep with the lights on
I've thought about switching to this method - problem I see is our nice molded-in battery trays which are not going to easily accommodate different sized batteries, leaving some compromises.
Cost on the isolator is not insignificant either.
