If it's time for a new battery, why don't you just increase it's size and not worry about it.
I have a 60HP 4 stroke and used to run a 27 series battery. I had lights, live and bilge pumps plus 2 Low HDS units on it. At the end of the day it was getting to be too much. I switched to a 29 series and haven't had any more problems.

I like the idea of that noco jump starter regardless of what size battery you're using.