Hmmm...maybe... *MAYBE* ... he actually just wants to spend time with his family and have them be proud of him for his new boat, etc. I would definitely have my radar on high alert though.
With what little knowledge I have of the situation, I would say my best case scenario for a conversation like this with my son would be maintaining safe boundaries for myself and the rest of the family, then not engaging in much argument and not telling him again what he already knows.
I am pretty sure that sometimes I sound to my son like the teacher sounded in the old Charlie Brown cartoons, or that old Gary Larsen "Far Side" cartoon that shows a man talking to his dog about getting into the garbage. The first panel is titled, "What We Say" and shows the man saying, "Ginger, you're a BAD DOG. I told you NO garbage. NO GARBAGE. Shame on you." The second panel is titled "What They Hear" and shows the man saying, "Ginger, blah, blah BLAH. Blah BLAH blah. Blah blah BLAH."
So in my perfect conversational scenario in my situation, it would go something like this:
Me: Wow, congrats on the new boat! Sounds like fun, but we do not feel it is safe for Bubby to go out when we know you are still drinking. Maybe another time.
Me: Sounds like a good time. We do have some plans for this weekend.
Me: It looks to me like you should probably have it looked at (or) What do you think? (0r) Have you put some XXX on it, etc.
Beyond that, let him figure it out.