On board conflicts
In your case just be patient. Watch him and figure out how you would do each task that he does now. For instance he may be bigger and stronger but as long as you are even a little agile you can do the same things your way.
So wait for something to go wrong and then help.
I have to admit that I single hand the boat even with guests on board. The only help I accept is when one particular friend is on board. He owns the same model boat and is really good at sailing as he has been crew on many winning offshore races. Others just get in the way.