Hey Mike,
The portable carports that you can get at Costco work very well. If you are not a member you can also get them at bi-mart just be sure to get one that has 4 side legs and not three. I lost a three legged one because of snow a couple of years ago, the tarp survived but the frame bent ca lapsing on one of my boats. Luckily the only casualty was one plastic folding guest seat.
Mike
These do work great Michael. I recommend that you stake the corners with a very heavy duty stake down. I've had them running around the yard in the wind. In wet climates they will also condense. I recommend a cotton canvas tarp over the boat to wick away any moisture and trap drips. Not a big deal but worth the trouble.
Mike, I had one of the covers with the tarp-like cover that lasted about three years before the tarp needed replacing. Then it collapsed from snow. A friend suggested getting an all metal carport and I found some on the internet and ordered one. It cost about $600 installed and anchored and was put up in about one hour. Now I don't worry about snow or replacing tarps. The carport should last many years. Just look on the web for carports to see what is out there.