Really clearly said the box had never been off before. So ask the op if he has x ray vision. And brush up on how carbs work. And the evaporative properties of gas.
The slower you go eventually it will shift into neutral. If you keep going it will shift into reverse. Get a manual or go to a dealer and have him explain this simple process to you.
Pretty sure that motor uses a rectifier only. So higher voltages are normal make sure you are using a good non sealed standard battery. That style rectifier uses the battery as the regulator so you need to be able to refill it.
You do realize how old that 4 cylinder design is don't you? And hard to believe it only used 3 gallons of gas in 4hrs of hard running. If your top Rpm at full throttle is only 4700-4800 rpm you might need a different prop.
