PR;
I always worry about getting to shore quickly in the event of an emergency. As for gas engines, I tell everyone only to use ethanol free gas only and when you finish running the motor, simply let the engine run out of gas so no fuel of any kind will remain in the fine jets/ports of the carb where it gums up which is the leading cause of engine failure paticuarly at low speed coming into the dock.
Use of small trolling motors in rivers with much current going against tide and wind has been reported no head way made which is why I do not advocate that style engine anywhere. As for a lake, different scenario. It depends on the situation.
As for the batteries I would suggest the use of a battery selector with quick disconnect. They are correct on the run as to the size of cable you will need. Stu and others please correct me if I am wrong but can you still run one cable from the negative ground of the battery to the second battery negative ground?
As for color coding, the yellow cable is now for negative ground on DC cables only so not to confuse them with black for AC which is shore power or 120.