With all the recent posts regarding folks replacing their heavy 8D batteries, thought I'd post the hoist/beam/trolley I fabricated last year when I replaced my old 8Ds with GC cells. Sorry for the poor lighting in back of the shop...
The hoist allowed this 65yo sailor to singlehandedly lift the 8Ds, trolley them over the engines, and set them down on engine room floor, to be later hoisted up through floor hatch using a step ladder and ratchet hoist. A similar design for your boat may save someone's back if your batteries are outboard of twin engines as on my Defever 44.
The first picture shows the hoist beam with the left end that would sit on top of the fuel tank, the right end would be C-clamped to the engine room floor hatch support beam (ceiling of engine room). A sturdy (300lb rated) fiberglass stepladder was positioned in the main salon straddling the open floor plug, with a ratchet cable hoist (come-a-long) attached to the top step. The third picture shows the right side of the beam and the path of the hoist cable around a 4" sheeve on its way to the trolley block. The second picture shows the left end of the beam with the trolley block that rolls along the beam, and the restraining line that controls movement of the trolley block.
Other than a few 6013 welding rods and paint, everything came out of my scrap iron pile....Wife refers to me as "Rube Goldberg" more than she likes!
Anyhoo.....hope this helps someone!