[Gary1]

You absolutely have the right idea. The only fly in the ointment is running two thirty amp, 120 lines into the boat. You can do it that way, but you'd be much better off running a single 50amp, 240VAC Hubble cable from the shore to the boat.

The reason I say this is that you'll be sure you're getting 240 from the power post. I can't even begin to tell you how many dual 120 receptacles I've seen wired incorrectly in marinas. To make sure you've really got 240 available, you really have no choice but to measure from one 'hot' lead to the other. If it's wired correctly, you'll see 230-240 volts. If you get a 'zero' volt reading, the receptacles are just a single 120 source, and it will do Bad Things to your 240 a/c system.

The second reason I'd suggest a single 240 cable is that more and more marinas are putting in the 240 receptacle and a single 30 amp 120 receptacle, so the option of running two cables just isn't there. My last reason is just a casual observation with no science to back it up: for some reason, 30 amp cables just seem to go away easier. I'm not sure if it's the contacts, the way the cables are produced or whatever, but they seem to fry themselves with little or no provocation and without warning. My guess is that it's because the receptacles' contacts get worn out and loosen up, causing bad connection.

Something else I noticed in your drawing is that you don't have galvanic isolators shown. If you're doing a major overhaul to your electrical system, bite the bullet, purchase them and install them. They'll protect your running gear and through-hulls in marinas that don't have good grounds. (And a lot of them don't!) They'll also help protect you from the idiot power-boaters who leave their power cords in the water, turning the whole area into one huge battery.

The other thing I notice is that you don't show a pair of 30 amp circuit breakers on the incoming, split 120 lines. The 120 also needs breakers just 'south' of the incoming lines, or otherwise your 120 systems won't be protected.

Sorry that my modified drawing isn't as neat as yours, but I used a paint program, not a cad program to modify it.