I'm not the trailer brake and weight cops and still maintain your TB will do ok with that boat, IF it's in good mechanical condition.
BUT 5000mi a year towing high profile (truck will think your 10' tall boat is 4-5000lbs not 3 due to wind resistance) on at least half curvy or hilly roads says get some trailer brakes to me.
Since you're still asking the question, I'm surmising that you don't have a lot of towing experience. This is almost as important as having brakes IMO. So if you don't have one, get the other.
Another thing, I'm not up in that vehicle's issues, but FWIW, I've known several people who have claimed that the TB and it's Buick sister are very riddled with issues. Common theme with our neighbor who claims they went through the mistake of 2 of them now. Second one they dumped after like 2 years. Buddy dumped one for an expedition that they've now had for 10 years or so. Couple others I just heard random complaining about.
This is of course conjecture, but nobody buys a TB because it's the coolest thing on the road, except maybe the SS, so they're looking for reliability and good service life and the consensus is it's not there. Just food for though. If you can get good money for it and step into a Tahoe, expedition or pickup you'd probably be money ahead vs sinking it into the TB.
