First off let me state " I am tired of buying boat batterys"
This probaly aint the right place to post this.
My old boat uses 4 group 27 deepcycle batterys and every year i need to replace at least one.
The other night one of the trolling motor batterys died.
Ruined the whole night.
This is my offer, i will cerakote your rifle, pistol or shotgun for a new group 27 battery.
If you have a connection and get them wholesale this is for you.
If interested pm me cause i hate buying batterys.
Thanks Clinton

I used to work for a Battery dealer and we had to go through some intensive training. One thing I learned was "unfortunately for your wallet" you should never replace ONE battery out of a group that is connected to one another. It usually brings the new one down in capacity to match the older ones-NOT the transverse.
Also, they "should" match in capacity, specs, etc.
If you buy a matched set of quality batteries they will last MUCH longer than what you are currently doing. I know the upfront cost stinks.
If you are keeping the boat, this is great advice, if you are thinking of selling soon then keep on keeping on.
I would consult with a battery expert on what you have, what your physical space for batteries are etc.