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On My 97 Outrage 17 I moved the oil tank into the console. Had no desire to add another battery in there.
So, I installed a battery disconnect switch so everything but the bilge pump was off when the boat was idled.
I also added a Blue Sea low voltage disconnect relay for all the accessories. That saves the battery from being run down by having lights, radios, electronics on all day.
https://www.bluesea.com/products/7635/m-LVD_Low_Voltage_Disconnect
I also added an on board single Marinco battery charger.

All together the above was less cost then a 2nd battery and had the added advantage of being able to charge the battery and get me started if I left everything on too long.