Grounding the battery when using outboard

Hi, I need clarification. Rewiring my boat, it has an outboard motor. The negative circuits are lead back to a grounding bus-bar, which then goes to negative on battery( as well as to the circuit breaker panel) . Do I need another wire from bus-bar to the waterlike with an inboard, where you lead a wire to the motor, and this provides a ground to the water. I have not hooked up the wires from the outboard charger, but when the motor is out of the water, that is not grounded either. Or am I overthinking all this? Is the reason you ground to the inbaord is to protect from stray currents eating through any thruhulls?

 

You're over thinking. You do not want the outboard casing grounded. You would then be introducing dc into the water as you said, stray currents. Your motor electrical circuits are already grounded through the DC negative wire. Grounding the shell of the outboard would just eat your outboard lower unit.

 

Is this an electric start outboard? what size? what is it? lets just get a picture of what you are doing here.