Hi all,I am a newcomer to sailing and recent proud owner of a Beneteau 343. Could someone here help me solve the following three mysteries?Mystery 1 - Both my starter and house batteries do not seem to hold a charge too well after each full charge. My carbon monoxide detector alarm malfunctions (beeps due to low charge) each time the batteries drop, and this is becoming annoying each time I come to the marina. No other devices were left on, other than the CO2 sensor and the bilge switch. Power terminals were all in the "OFF" position. Can anyone point me in the right direction as to what would be the possible cause? I know that a battery tends to drain while in storage, but I would expect the drop would be negligible over a one week period. Mystery 2 - My zinc attached to the prop disappears every few months. A new one was installed last October. In March, I hauled out the boat and the zinc was completely gone. A new one was again installed. Just two weeks ago in late May, I hauled out the boat again and guess where the zinc was? Gone AWOL again. Other boat owners in the same marina at the same dock don't have this problem. Mystery 3 - Without shorepower, I switched on the stereo on my beloved boat with both the house and starter terminals in the "ON" position. I then switched the house battery to "Off" and the stereo remained on. I then turned the common terminal to the "Off" position and expected the stereo to die. The stereo remained on. Man this is getting weird. My local Beneteau service agent recommends that I install a Galvanic Isolator. Will this solve Zinc problem, given there are other weird problems? Any doctor in the house? Please help!