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Sold at Lowe's and HD. Around $35, or less, if on sale. I've heard they work, but have no personal experience.
Actually, neither one of these is the one I was thinking about, but, they get the idea across.
50 lb limit, here:
125 lb limit, here:
using two boat type winches, one on the left and one to the right, such as shown in the first answer that are attached to straps that will hold three kayaks on the front wall of my garage.
The strap system is similar to NRS' item #1518, but is a triple set up. There's even room for one to sit on the floor.
Hubby even hung a tennis ball, from a beam, that will touch my windshield when I'm at the point to stop so the boats will not be touched and there's still room to walk in between the boat and vehicle.
It's been hanging there for several years and frees up floor space for the other boats. We've never had any problem with it whatsoever. Works great for us.
Here are some shots of a variation of my hoist system, made from parts available at any hardware store.
I've built seven of these now, four of my own and three for friends, and unfortunately, the only one of which I have pictures posted online doesn't make ideal use of rope (the reason for this, and a potential solution to the problem which would be better than one adopted, are described in the text beneath the photos). The main difference between the pictured method and my standard one is that with my regular system, a single hand winch pulls a single rope, and that rope splits into two ropes which do the vertical lifting. Thus, turning the crank raises and lowers both lifting ropes exactly the same amount, with no adjustments being necessary.
For a kayak, you might use a pair of slings instead of the wooden gunwale supports that I use for canoes. If you need to get the boat right up to the ceiling, attaching each sling to a spreader bar would do the trick, so that the strap could be very short without squeezing the boat (in that case, the center of each spreader bar would be where the lifting ropes attach).