It appears that everything is coming together and I will be able to install the new water heater tomorrow. The plan is to install the new one, re-plumb the coolant lines to the heat exchanger in the tank and refill the coolant. The fresh water tank still has winter antifreeze in it so I was not going to re-plumb that to the hot water tank until after we are in the water and I can flush that system. Dumb question is.........can I run the engine without water in the hot water tank or will that damage the heat exchanger? I checked the Seaward website (which is Whale pumps BTW), they had nothing to answer that question.