As far as the initial question "when is a boat
a yacht" it varies drastically on who is talking and what they are talking about. basically everything from a pleasure boat
to an elegant vessel decked out with gobs of brightwork and bronze
by someone that is totally clueless about boat to someone that has an appreciation of what makes a fine boat...if i was forced into a corner and had to come up with one simple sweeping statement i'd say " A fine boat that is a cut above the average production boat"