Trailer Tongue Weight and Sway
4 wheel trailers are much easier to tow than a 2 wheel, so am surprised you are having problems.
If the factory rates the hitch at 200 lbs max, it may be marginal for towing your boat. Don''t know what your weight is boat and trailer, but would guess at least 3000 lbs. 260 lbs tongue weight would be about right. If the boat and trailer weigh more then you need more weight on the tongue and probably a heavy duty hitch bolted/welded to the frame to carry the load.
There is an excellent book on the subject "Boat Trailers and tow vehicles A Users Guide" by Steve Henkel. You can probably find a copy at Barnes & Nobel or Amazon.com if you look. Lots of good info for the trailer boater.
Merry Christmas to you and yours!