A couple of things to check
Nathan, I agree with Michael, it sounds like the solution is more than just adding a solar panel. Is your boat on shore power all the time? If so does your charger have mutiple stages? If your charger is broken it can fry your batteries in short order. Try the following: 1) Check that your batteries are fully charged. Use a sensitive voltmeter or a hydrometer to check the specific gravity of the electrolyte. If not your charger may not be working right or your batteries may be toast. 2) Verify that your charger is putting out correct voltage for your batteries. If not it is bad or there is excessive resistance or voltage drop in the charging circuit. 3) Check the voltage in your batteries before you try and start the engine and while you are trying to start it. There should be a drop but not a precipitous one. I have a two bank setup on my 37.5, 4 group 27 house and 1 group 30 starting that would never get fully charged. Then one day my charger checked out, the thing just burned up. What happened was that the charger was putting out more current than the wire connecting it to the batteries was rated for at the distance it was from the batteries. Add in an additional junction box from when the P.O. moved it and it was just waiting to break. I put in a new charger installed with the correct wire guage for its location and all my charging problems went away. It only takes a corroded cable end or dirty connector to make things stop working so check those too. Jim "Prospect"
