I think it's a good idea, but you're going to have to stress that there isn't ANYTHING else wrong with the boat other than what you've documented. Many people will sell a boat in that condition as "MINT" (aside from the canvas rip). Otherwise you're only pointing out flaws in your product while others are hiding theirs.
I mean, which would you rather buy... A boat that is claimed to be in mint condition, or a boat that "only has a few flaws."
Something like this would be more beneficial if it were like a Barret Jackson rating or standard of quality thing, where it was known nation wide and they could rely on it. Then it would carry more weight, and it should probably conclude with an independent survey.
*** Aside ***
If that's a boat you're selling you should probably have the cover repaired. It drives me nuts when someone is trying to sell a high-dollar item and there is a noticeable, ugly flaw that is relatively inexpensive to fix. The scratch in the hull may fall under the same category.