Any restrictions on engines?

[Ian Curtis]

Originally Posted by StevenB

I love how the trolling thread has been derailed into something useful.

I remember reading a model rocketry book which was adamant that the propulsion was a "rocket motor", and not a "rocket engine". But I see now that Estes calls them "engines".
Wikipedia treats "motor" and "engine" as effectively synonymous, at least until someone here goes and edits the article.

A rough rule of thumb I have heard for rockets is that solid and hybrid rocket engines can be called motors without anyone looking at you funny. However a liquid rocket engine cannot be called a motor without someone raising their eyebrows.

All I know is I have an outboard engine on my motorboat...