Your other option would be to get THREE more stock packs. By getting three, you double your run time by wiring them in parallel and keep the boat balanced by running one on each side. That would give you one set in the boat while the other set is either charging or waiting to be used. The down side to this is that you would need to have someone(if you don't want to or know what's needed) solder you up a "Y" harness so that the two packs both feed the speed controller and, indirectly, the motor