What is this?

[Jkeebs]

I am requiring my boat with lithiums and am wondering what this box does? 2018 z18 thanks!

 

[Andrebass]

My guess
A charger

 

[ditchpickle98]

It's either a shore power charger or an alternator charger. The purple wire coming out of it makes me think it's an alternator charger, so it knows when the engine is on and it can start charging the batteries.

 

[Andrebass]

Look on the batteries for the same colored wires and fuses. See where the purple wire goes and ditchpickle98 might be right.
Next time when on the water and engine is running check to see the red light is on and check voltage at trolling motor batteries.

 

[jerry shack]

I am requiring my boat with lithiums and am wondering what this box does? 2018 z18 thanks! View attachment 2748

It's a power relay box

 

[Tim_C]

It looks to be a power invertor. The part is labeled 2015 and your boat is a 2018. Who Added it? Ask them.

 

[Lobsterclaw]

Jerry has got it I think. There is one on my boat. It would cut off power to my trolling motor when the ignition was turned on. May be a type of DC to DC charger by the smaller fused wires that connected to the batteries.