While I agree with being prepared which to me includes having someone there on site to assist, I'm also not letting the marina off as easy as some of you are. I've read in this thread somewhat casual statements regarding extended power failure. If it's power outage caused by a storm and the entire area without power, I can accept that. However, if it's not that then the other reasons are unacceptable meaning any power outage just at the marina. Here we've got a marina saying they shut the power off due to low voltage. What? What are they talking about? They have a responsibility to get it repaired, functioning quickly. This isn't a qualified "act of God" or any other disaster. It sounds like a marina with an inadequate power system or some other issue. I'd also expect them to check my boat for me daily and let me know how it's doing until they have their problem fixed.
To the OP, did you get any further explanation as to what is going on and why?
Do you know that the marina is slacking on this issue or are you just guessing? Is there a problem getting the electrician there quickly? Is there a failed component (transformer, special breaker, panel, etc.) that has to be ordered? Was it over a weekend or holiday when all the supply houses were closed? Did a storm or a runaway boat damage the dock or wiring?
I'll bet the slip lease does not guarantee uninterrupted electrical power 24/7. The OP is fortunate that they sent him a notice. They didn't have to do that and many would not have.
It's far to easy to blame someone who doesn't have the opportunity to tell his side of the story.