Re: UK greencard holder living in US, buying a US boat to keep in US HELP!
NightOwl, an LLC will not help him. The LLC cannot legally own a documented vessel unless the LLC is majority-owned by US citizens. Try to dodge that requirement, and they can charge you with criminal fraud and eject the non-citizen from the US on a pemanent basis, and that's just to start.
Panda, your choices are to Cali register the boat, which many Mexican officials may accept since Cali is their neighbor, or UK register the boat, in which case it has to leave the US for at least 15 days every year while you apply to get the cruising permit to bring it back into the US. Which is normal but not guaranteed.
I'd suggest corresponding, in writing, with some Mexican authorities to see how they feel about a Cali registered boat coming to visit--in writing, because we all know how arbitrary stray uniforms can be, on any border.