Re: hoist ideas
Use your judgment and be safe. I built mine with doubled 2x10's running up the sides, then three 2x10's on their side running hroizontally across. These were held in place with short 2x4's screwed to the verticals to create a sort of yoke that the horizontals sat inside of. The verticals were lashed to the sides of the (pontoon) boat and had 8 foot 2x4's going fore and aft at a 45 degree angle to the ground, where they bottomed in shallow holes. The 2-ton come-along was hooked to a chain which was around the horizontals, the chain held in place with many deck screws (although it won't slide once the load is there anyway). All of the lumber pieces were assembled with many, many deck screws. I was pulling a 3.0, so it was light compared to yours. The way I built it, it wouldn't move. It sounds like you'll be driving the boat out from under the hoist, so it has to be free standing. Shouldn't be difficult to set up. No matter how strong it is, keep the body parts you like out from underneath!