My hunch is this is not an intentional scam, but maybe not what it tries to appear to be. I think caution is warranted, but I don't think it is set up to intentionally rip people off. Would be kind of an odd niche scam to run. My gut on it is that it is an individual or very small team trying to make a buck by selling refurbished motors. They might have a hard time following through on promises, but not intentionally.
That is mostly instinctive speculation - not fact. I would be reluctant to avoid doing business with someone simply because their prices are low. While it does raise the question of why they are low, there might be perfectly good reasons. I don't believe the reasons they give on the site, but I am also not familar with how the OB motor business works.
I would call and just be frank about your concerns. If they are dodgy about the answers, then, there you go. If they are legitimate and just trying to make a living, they will learn something from the call that might help them improve. Of course, if it is a deliberate scam, they will also learn something that will help them improve the scam, but I just think it is better to have the conversation than to speculate.