Hello There. I currently have a 96 Sea Ray Sundancer 7.4lt single engine with a Marine starting battery #1 and a house deep cycle battery #2 it is 800CCA, 185 Reserve, 105 Amp Hrs. My factory charger is a Mariner 20 amp original equipment. According to Mariner this charger constantly charges and never shuts off. Its putting out 3-5 amps according to the needle gauge on the charger. The past 2 years I have always left the charger (DC converter on the breaker panel) on at all times with the battery switch on both batteries when on shore power. We are on the boat for 3-4 days at a time using shore power. When we leave the boat for a few days should I be leaving this charger on, or turn it on when we return for a few days. I have noticed that the electrolyte needs to be topped up in the deep cycle battery periodicaly. This battery also doesn't have enough power to start the engine I always use #1 or switch to both when starting. The batteries are 2 years old ,do you think the house battery is toast, as 3-5 amps never seems to fully charge it even after a few days of charging. My volt meter shows house battery at 13.9 volts with charger on. Any help would be really appreciated. Steve.