I have twice removed and replaced my 250# engine using the main boom. I pick the point on the boom from which the engine will be suspended, then rig a snatch block on a line attached at the end of the boom and running forward to that point. Run the jib halyard through the block and down to the engine, and guy the boom over the pick point. There is no bending strain on the boom. Hoist with the jib halyard winch. When clear of the companionway sill, I placed a short 2x12 over the sill extending forward of the engine, and support that end from the hatch runners. I was able then to slide the engine aft on the 2x12 til it was clear of the cabin trunk, repositioning the snatch block as we went. From there we could swing it on the the dock. If your engine weighs too much for this arrangement, and there is a haul-out facility handy, you could hire them to pick it out and have your buddy tow you home.