I'm using a metal carport to cover my 16' Bluefin tinnie w/ tiller steered 30 horse Evinrude. I had some spare metal panels with which I covered the sides to within about three or four inches from the ground. both ends are open. I live in southern New Mexico where temps reach well over a hundred degrees in the summer and seldom dip much below freezing in the winter. I doesn't rain often but rainstorms can be fierce and even though the boat pretty much fills the carport from end to end, even a blowing rain doesn't cause enough water to hit the boat to even make a puddle in the floor. We usually don't get enough snow to worry about.
I think the carport itself cost somewhere between six and eight hundred dollars, NIB, several years ago and even had I had to buy the side panels the cost would still have been well within your budget constraints even today.
CONS: In the hot weather the metal sides and roof transmit enough heat to the boat that the aluminum parts of the boat get uncomfortably hot to the touch. At certain times of the year the sun shines fully on the outboard motor in the morning, so I try to keep a canvas cover on that to avoid UV and heat damage to the hood. I no longer have any soft vinyl seats in the boat, but if I did I would probably want to take them out and store them in some cooler place or at least cover them with something to insulate them from the heat inside the carport.
Other than those considerations the carport has been ideal for me and a far better solution than the vinyl cover I used to wrestle with every year.
Hope this helps.
