Inboard boats. It has nothing to do with the motor though. It just doesn't physically work with outboards the way the motor is positioned on the boat.
A bag of potatoes could be used on an outboard, just not effectively. A better way to put it is that it isn't used, not that it cannot. Clearly it could.
You have a hard time listening. It could not be used with an outboard motor just like you couldn't have a hard bed cover on your pick up truck while you pull a gooseneck trailer.
I know nothing about inboards, but on outboards, there is a lever that keep the motor propped up after you trim the motor up when it's in transit. Is this one of those, but for outboards? I'm reaching.