^^^^^^ This ^^^^^^raycarlson wrote:JUST TAKE your rig and boat to the nearest walmart etc late at night and practice backing around the lot.
Boats are strange things to back up anyway, as they're curved, and wider than the tow vehicle usually (wider than the mirrors, often), so what you see in the mirrors doesn't give as much of a sense of what's happening as it should. An RV, on the other hand, is the same width as the boat (both 8 ft, typically, plus mirrors), and gives a better visual.
The trick to backing, using mirrors or not, is to visualize the track the trailer tires are taking, and where you want them to go. The boat is irrelevant - it's the tires you're steering. Visualize the arc, and learn to put some in and take some out (tighten or loosen the radius the trailer tires are following) then maintain the arc, which is defined by the angle between the tow vehicle and the trailer (zero when straight). Visualize where you want the trailer tires to go, and put enough bend in the rig, and hold that bend, so the tires follow that arc. If too tight, take some out. Not tight enough, put more in, and in either case, follow the trailer with the tow vehicle once you've made the correction.
Learn how to start straight, put some bend in, then follow it so the angle doesn't change, just like taking a bend going forward - the trailer to vehicle angle remains constant. Starting straight, if you want to back to your left (driver's side), you turn the wheel to the right (forget the hand on the bottom of the wheel stuff) to start the rig bending that way, then as the rig starts bending, turn the wheel the other way to slow the rate the rig is bending. Turn it enough and you will follow the trailer in a constant arc. Turn more than that and you will 'take some out'. Keep taking some out, and you'll come around in front of it and be straight again. It's a matter of visualizing what the whole rig is doing while you're steering the trailer tires around like a wheelbarrow, including the steer axle of the tow vehicle.
In fact, that's a good way to start - going forward, establish a gentle turn, then back up and try to maintain that angle as viewed through the mirror (again, big empty parking lot). From there, start straight, back up, intentionally put some bend into the rig, then turn the other way to follow the trailer and hold the bend. More advanced is to make small corrections to increase or decrease the bend, and then hold that bend.
It's easier with a short tow vehicle and a long trailer, but the principle is the same for any trailer/tow vehicle combo. With the long overhang of an RV, it will react a bit faster, but at least you won't have to put the tires in the water when launching.
It's a skill well worth developing, and I think you'll find it's not as daunting as you imagine it will be if you can get some practice in an open area. And learn how to use the mirrors. 
(disclosure: I drove trailer trucks for nearly 15 years, many moons ago, so maybe my view is a bit jaded
)
and trailer rigged for actual use is going to weigh in at more than 3500 lb. It has some permanent ballast, which the 
does not, and of all the folks reporting the actual weight of their boat/trailer combos, I don't think I've ever heard of anyone's rig coming in at less than 4k, including the 
Ron.
