I had the plant design/mfg/install the hoist and mast/boom. *So the best is to draw out what you want, take it to a fabrication/welding shop that does this type of work.* Ask around the yards/marinas for recommended shops as the tube thickness, the plate support, welds, angles and winch are all important.* Both the hoist and mast/boom cost about 2 grand to have made, so its not cheap.* I tend to go to the commercial docks/yards as they have built hoist/booms/rigging before.* ***
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A hoist would probable fit/look better than a mast and boom on your boat. By hoist I mean a round tube that is bent about 35 to 40 degrees that can swivel/turn on a base. I used 4 round aluminum thick wall as 500 lbs is a lot of weight when leverage out there. **The hoist or mast/boom cost about 2 grand and not something you will be taking off and on.*