I can tell you from experience that running a marina in/near the eastern Sound is a very difficult business. Even with 100+ deep water slips that will handle boats 30 ft. and over, there simply isn't enough income even if the place is always just about full with seasonal and transient boats. You really need ample space for winter storage, a very well-equipped shop and a staff with factory training. Simply renting winter storage space probably won't do it either unless you have the equipment and skills to step/unstep masts and remove/reinstall engines. The costs associated with all of that are very high. Workman's comp insurance in Connecticut is very expensive as is liability coverage in what can be a fairly hazardous workplace.
A gas dock is a valuable income producer but is also a maintenance headache and expensive to insure. Even a minor spill in a high profile harbor like Essex will draw the attention of Connecticut DEEP, which will ask about the training you provided to those minimum wage-plus-tips youngsters you have to hire during the summer. Do you have a written manual and the containment equipment needed to contain a spill?
On the Connecticut River (and other New England rivers)just cleaning up winter debris can be a time consuming and expensive process that produces no income. If a seawall has been damaged (common on the river), hire an attorney, file a permit and wait. If you repair or replace pilings or dredge to recover lost dock space without permits, the fine can be overwhelming for a small marina like Essex Island.
The Brewers business plan is pretty sound, part of which is to maintain their customers' boats. Sure, Brewers is expensive but they have to be to maintain the quality of the marinas they operate.
I can see why the family that owns Essex Island wishes to retire. There are a number of other marina/boat yard owners along the river who would also like to retire if they could sell at a decent price.
Bill