Every boat/engine/fuel/plug setup is slightly different, so it's difficult to provide an exact recommendation on where a needle should be set. Compounding this are temp/humidity/air pressure differences.

I have no idea where mine is, I have not screwed it in and counted since the first day I ran it. When I go to the pond it's usually morning and a little cooler than when I last ran it. I open the needle 3 or 4 clicks and run it. As the day progresses and it gets warmer, I gradually lean it out 3 or 4 clicks. I suspect I'm still running rich because the only time my boat has died is when it flipped due to hitting a wave or a bouy. I'm happy running rich, it means the engine will last longer and my boat won't die during a heat from being too lean.

Here's my thoughts on trying to squeeze too much out of an engine by leaning it out. Most of my running time is racing. When racing, my highest priority is to finish. Finishing, but being slightly slower is much better than having a boat that died on the last lap because it was too lean. I've watched a huge number of boats fail to finish heats this summer due to being too lean. In one of the heats at our last club race, I was in a comfortable second place. The person in front of me was about the same speed, perhaps a bit faster, so I was content to let him stay out in front. Part of my reason for doing this is he often makes mistakes when I pressure him. As he was nearing bouy 4 on his last lap, his boat died, too lean. I just cruised past and collected another 400 points.

The post before yours provides one guideline for setting the needle. If the engine starts slowing down at full throttle as the tank is getting lower, it's too lean. Mine gets slightly faster as the tank gets empty, a sign that I've got it set comfortably rich.