Dual battery - Unknown ground wire to batteries

[Robbie - Bama]

2016 Yamaha 242 S

I just recently swapped batteries due to low/high voltage warning. When replacing batteries, I located a ground wire that was not hooked up before, but I can tell it had been previously. New boat to me and my dad, the previous owner can’t recall where it hooked up to.

Facts:
- starting battery has two 4-6 gauge grounds going to engine compartment
- house battery did not have a big ground, other than two for the amps and 3 smaller wires that all appear to be for audio system.
- unknown ground is smaller gauge (maybe 10-12g) and goes into engine compartment, into another larger wrap of wires.

 

[FSH 210 Sport]

2016 Yamaha 242 S

I just recently swapped batteries due to low/high voltage warning. When replacing batteries, I located a ground wire that was not hooked up before, but I can tell it had been previously. New boat to me and my dad, the previous owner can’t recall where it hooked up to.

Facts:
- starting battery has two 4-6 gauge grounds going to engine compartment
- house battery did not have a big ground, other than two for the amps and 3 smaller wires that all appear to be for audio system.
- unknown ground is smaller gauge (maybe 10-12g) and goes into engine compartment, into another larger wrap of wires.

How do you know it’s a ground wire ?

 

[Robbie - Bama]

How do you know it’s a ground

It was labeled inside the plastic wire loom. I’m curious as to whether it should go on the house or starter battery. Right now, the starter only has the two negatives going to the motor.

 

[FSH 210 Sport]

It was labeled inside the plastic wire loom. I’m curious as to whether it should go on the house or starter battery. Right now, the starter only has the two negatives going to the motor.

Well, all the grounds should be connected together….

 

[Robbie - Bama]

Well, all the grounds should be connected together….

Are you saying it doesn’t matter whether it is connected to the start vs house?

 

[FSH 210 Sport]

Are you saying it doesn’t matter whether it is connected to the start vs house?

Yes because the start and house batteries grounds should all be tied together

 

[Robbie - Bama]

Yes because the start and house batteries grounds should all be tied together

That makes sense. Thank you.

 

[Madman]

Yes because the start and house batteries grounds should all be tied together

So that’s a question that has been bothering me. Electrical is not my strong suit, but I know just enough to be dangerous. I don’t like how Yamaha wires the batteries and thought it would be nice to consolidate all the grounds. It would simplify battery installation, but I wasn’t sure if I’d need to isolate each battery with separate buss bars. I’m guessing that I’d need to connect the negative from both batteries to the buss bar?