You could do it with a trailer winch. That could run to sets of 2 :1 or 3:1 purchase.
My garage hoist, for a smaller kayak (Maui), is 3:1 and I easily hoist that weigh by hand.
This hoist keeps the boat inverted and places the carrying loads on the cockpit side rails just as though on the truck roof rack. This is ideal.
The Hoist: Two overhead pulleys are attached to heavy duty lag hooks threaded into joists. It's a double line system that has two 3:1 purchase blocks below. It has lines passed through scuppers and a pair of dowel cross members (these could be stronger or be of another material), but this works for my Maui. The hoist lines feed to the wall and then down to a pair of cam cleats. I also tie this off for security.
(Drawing / details at the bottom of the post)
I pull the line through the scuppers (The tail of line hanging down allows me to easily pass the line down through the scuppers and then pull the loops through) and then pass the cross members through the loops. I have also added two "humps" of tape to mark and keep the dowel centered. No knots to tie... just two cross members passed through the loops.
I then simply hoist the kayak up off the roof rack. The load is balanced and stable.
The dowels are what I had on hand and could be stronger, but they worked for proof of concept.
The double line system is easier to rig and allows you to pull the lines down when setting up to hoist and adjust height independent of the opposite end while hoisting. I had these triple blocks, but note that doubles there is all that is needed.
Boats without single / centered scuppers aft might have to use a beam setup to split the line to both (cart) scuppers.[/quote][/quote]
