I bet it's more like 2000 lbs (like my Plymouth voyager)
if you have brakes on your boat trailer. Without brakes...they recommend
1000 lb max load.
BTW...the Toyota Sienna has a 3500 lb tow capacity.
My load is 1200 lb sailboat, 400 trailer and about 70 lbs for outboard plus
whatever. I'm maxed out but have installed a transmission cooler to help.