I want to add a second battery at the front of my 18 foot pontoon boat to run a trolling motor that will mounted on the front.
I would like the main motor, a 70 hp Evinrude, to charge the trolling motor battery.
What gauge of tinned marine wire would you suggest? I assume stranded wire would be best.
If you want your 70 hp Evinrude to charge both batteries, it may be easier put the second battery at the stern of the boat and connect them together with a boat battery switch system, which you can find our on sister marine electrical site.
This will allow you to select which battery the engine is starting from and also help prevent a dead battery after too much trolling motor use.
Run the trolling motor leads to the rear of the boat and use circuit protection as close as possible to the battery for the trolling motor.
The cables that connect the batteries are short and there is no requirement to have circuit protection on them since that can be used as part of the starting circuit.
Never use the frame of the boat as the path to ground. It will cause SEVERE galvanic corrosion.