Batteries in parallel for reserve capacity

I am currently running 3 Humminbird Helix 9’s in my boat. Near the end of a big day of fishing i am loosing power to the units. My current battery set up is one starting battery and one house battery for electronics which is a few years old, Not linked together (One optima blue top(AGM for starting) and one conventional marine battery)

My question is….if I buy 2 new group 24 batteries with 120 min reserve capacity and hook them in parallel will ultimately double my reserve? As well with them being hooked together my Yamaha 115 should charge the batteries a bit while i am running around the lake?

Thanks Dave

Are you saying the 2 new group 24s would replace both your single house battery and your single starter?

If yes, I wouldn’t recommend that from the problem your trying to solve. right now your worst case scenario is loss of electronics. If you have them linked this means that your starting and house circuits are no longer isolated. After a long day of fishing your worst case now is the motor not starting. That’s anywhere from an inconvenience to a real safety issue.

I’ve seen some of your other posts and looks like you’ve got a lot of load to care for and space is a challenge. I don’t know your boat so take this with a grain of salt and correct where I’m wrong.

Batteries:
3 36v TM
1 starter
1 house

“If” I had the room and budget I would add the following chargers:
MK 1 DC that takes overflow from the starting circuit to the house battery
2 bank 10-15 amp AC charger for starter + house.
3 bank 10-15 amp AC charger to cover your TM batteries

Additionally, I would upsize my house battery if there was room

Thanks for the comments. I recently was able to turn my optima starting battery sideways and push to the back of the compartment. This allowed me to get a new house battery with 210 min RC in the compartment. This is an additional 50% more RC than I had before. I believe I should be set from here on out.

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I got a skeeter wx2100. 4 batteries total. 3 for the 36 volt Ulterra. One for the electronics, livewells and lights. I run group 31 AGM’s. I also thought I would maybe need to add an electronics batt but never did. Never had an issue. I have the MinnKota DC charger but that only adds to the trolling motor batts after the starting batt is over 13.5 volts. I also have 2 helix 12’s and a 10. At least one 12 and the 10 are on all the time. Never have seen my voltage below 12.5 volts. 4 years and never had an issue starting the F250. Never had my Helix’s cut out when starting the big motor either.