What you seem to overlook is sleds and outboards have one thing in common. Constant throttle opening. This makes open loop EFI a doddle.Sleds have a CVT which allows a narrow band of rpm but a wide range of operating speeds. Outboards are off or on, like the 50cc Aprilia Orbital scooter.
The ECU will have trouble coping with, off/on part throttle applications not to mention the hot/cold pipe. Not unless there is a massive jump in affordable computing power.