Thanks for the great drawing!
I'd like to add a couple of comments.
First, it's even better to lead the mainsheet to the boom exactly where the engine is attached, instead of at the boom end. This keeps the boom in pure compression, with no flexing loads. With our small engines and oversized booms, it probably won't matter much, but better safe than sorry!
Second, be sure to have the mainsheet (or some other boom control line) cleated to keep control of the load as it swings out. I watched one horrifying/hilarious video of a couple who didn't do that. As they started to swing out the engine by hand, the boat heeled, causing it to swing faster, causing more heel... you get the picture. Out of control positive feedback. They quickly lost it. I thought sure they were going to dump it in the water. But, by blind luck, the boat went over so far that the engine hit the dock, rolled onto its side, and lost its lifting hook, and the boat righted itself leaving the engine on the dock! It all happened in a flash, leaving a stunned couple.
