I purchased a Hunter 356 in 2016 and replaced the water heater within the first year because of strong sulfur odor and grey to black color in the hot water. The replacement was a Kuuma 6 gallon heater with an aluminum tank. Now, five years later, I have the same problem -- sulfur odor and, when I drain the tank to flush it, black water. Draining and flushing reduces the odor, but only temporarily. I believe that the aluminum tank is reacting with the water in our marina. I have followed previous postings on this topic and know that Peggy Hall says the permanent solution is a new water heater, ideally with a glass-lined steel tank and an anode to protect the steel. So far, I have not found one that will fit in the space available. I have found one with a stainless steel tank and wonder if anyone has any experience with or recommendations about that as an alternative.