Actually, Jim, none of that is true for many if not most sailboat engines. By that I mean most sailboat transmissions are not "cooled" by anything related to the engine.(In fact all that I have ever owned or worked on were not cooled by the main engine cooling system) Some are lubricated by shaft driven pump that is driven by the engine input shaft. Others are simply "splash" lubricated. Splash lubrication is by far the most common form of lubrication on small sailboat transmissions. Most splash lubed trannys can be allowed to freewheel without burning up.
Also I have yet to run into boat with a marine engine that has a switch that requires you to start in nuetral. They may be out there, and you may in fact own one, but I have never seen one.
BUT is freewheeling a good idea? NO. even if the transmission doesn''t burn up it does increase wear and tear on the transmission parts and besides freewheeling creates more drag.