While I don't think it's particularly necessary for a recreational boater to practice every "engine out" scenario he can think of with his boat, I do think that he should have the common sense--- or practice having the common sense
--- to recognize a situation that is beyond his (or her) limitations.
The example posted by Della Rose above is a good illustration of this. Instead of stubbornly plowing ahead with a determination to get the boat to the dock no matter what, if the boater had realized that the challenge posed this particular time by wind, current, etc. was outside his ability to handle he could have backed off at which point several options open up to him. Go to another dock that's easier to get to, think the situation through and come up with a better plan, ask for help, etc.
There is a phenomena in flying that, for want of a better term, I call "landing tunnel vision." While not limited to newer pilots, it can be quite common with that group. The two times I've come close to having an accident in an airplane were when I was a passenger with the same relatively new pilot. For a variety of reasons, he felt he was inherently safer on the ground than in the air so he was determined to make the landing work regardless of the situation. So instead of going around and trying again, which in his mind would have simply prolonged the uncertainty and even fear of remaining in the air, he was absolutely determined to put the uncertainty and fear to an end by landing the damn thing the first time no matter what it took to do it.
Sometimes it works, but sometimes the pilot can get into some very nasty situations with the extreme result being a crash or an out-of-control situation on the ground.
I think boaters do this too. They are so determined to get the boat into the slip or up to the dock and thus end this uncertain situation with current or wind or whatever that they will press on even if the situation is deteriorating rapidly.
My wife and I have a policy, perhaps as a result of our flying experience, of backing away if a docking or some other maneuver begins to look like it's not going to go the way we want it to go. We often have current and winds to deal with in our marina and while we usually get it right the first time these days, if I've misjudged the current or the wind or our speed or our rate of turn or all four, that becomes pretty apparent fairly early in the docking process. So rather than try to "fix" it, which in our case would usually put us in a position of having to fend the boat off a piling and physically force it to line up with the slip, we simply "go around"---- back away before things get bad, go back out into the turning basin, and try again.
But to do this one has to be very cognizant of their limitations and also have the ability to recognize early enough that things are not going according to plan while there is still time to back away and try again. Or return to the safety of open water and come up with a Plan B if it becomes obvious that Plan A isn't going to work today. We have gone to another slip in the marina when very strong adverse winds simply made it too difficult to get into our own slip with the boat handling skills we had at the time. And we would do it again today if we were faced with the same situation.
I have noticed through the years that nobody pays any attention to a boat that backs away from a slip, goes out into the fairway or turning basin, and comes in for another try. But EVERYBODY in the marina looks up and watches at the sounds of shouting and crunching.