Wait so you don’t want the boat to be able to start on sound system setting? My current setup is 2 batteries, stock battery and added a 2nd deep cycle. They are tan to a dual switch (1/2/both), 1 is starting battery, 2 is deep cycle…when I launch I start and run the boat on 1, get to the sand bar and switch it to 2, if that dies then I’m done listening to music and I switch it to 1 when I go to leave. However I’ve cranked off 2 before when I’ve not listened to the music for very long, is that not the correct way to do that?
More then likely your draining both batteries equally in your situation. I could be wrong, but if the boat starts (stock it's on house battery) in your sound system switch setting that tells me your house battery is still being drained. Only true way to tell is multimeter test it under load and see if it's truly off.
So I have mine set like following:
A:House battery positive
*Starter and bilge pump direct to terminal
House battery negative
*All stock grounds, and one ground from ss1
B: Sound system 1 (ss1) positive
*4 Guage wire to ss2 battery
*4 Guage wire to Perko #1. Sound system 1 negative
*4 Guage wire to house battery negative
*4 Guage wire to ss2 negative
*0 Guage wire to distribution block
C: Sound System 2 positive
*4 Guage wire to ss1 positive
Sound System 2 negative
*4 Guage wire to ss1 negative
Now here's when mine gets tricky.....
A
erko switch #1 terminal
*positive from ss1
*0 gauge wire to distribution block(amps)
B
erko switch common
*independently ran head unit power wire
C
erko switch #2
*all house battery connections that were stock except starter and bilge.
So what I have done is put all my sound system on Perko switch #1. This way on my #1 sound system only works. With head unit on the "common" terminal it works on either [HASH=6677]#1or[/HASH]#2 switch. All house functions (conext, blower, lights, etc etc) are on #2. So when I'm driving boat I'm on "All" position. So everything works. At sand bar I'm on #1 for only sound system. This way my house battery is always not used. Notice house battery is not hooked to Perko switch.... This is so I'm 100% positive it will not drain. Starter and bilge are direct to house battery. So yes it will always start. Even with battery switch off. Might be a crazy wiring, but it works for me and has yet to leave me hanging
Edit: What I really need to do is wire in 2 independent switches. That way there is no chance at all of battery splitting loads with house and sound system. Just haven't done that yet ??