I have a 22' cruiser, the Mary Ellen. It has twin 40HP Hondas' with the shore power option which includes a charger. I keep it powered up during storage. I recently decided to look at the water level and found it to be low in several holes. I added water and thought I would have the batteries checked at Les Schwab. They both checked out as good batteries. I have 76 hours on the engines and the boat will be 4 years old this July. I am wondering how often others have had to replace the batteries? They are deep cycle batteries.