lots have been said about the over the top drinking by people in charge of a boat but I want to add this; you're chartering from them right? rather than a company; so they've had free bed and board for the duration of your holiday plus what they're making on the charter fees so in my mind that's enough. I'm a Brit so I know we have a different attitude towards tipping than some here but I wouldn't be giving any tip at all, in my opinion they've already had that, and some.
Or to say it another way, you are vacation in their home. These are owner/operators. Have some respect and tip according to the local norms. You don't have to like it, that's why Motel 8 exists.
