[C320-list] Electrical Problem

[Joseph Aberdale]

I have a very perplexing, troubling electrical problem that I would  
very much appreciate your help with.

My 2002  320 has two 4D banks of Interstate batteries that are 4  
years old. For the past month I have been experiencing the  
following.  If I don't start my engine once every 3 days, there is  
not enough power in the batteries to turn it over to start. I then  
have to use shore power to start it. Recently, I motored the boat for  
2 hours to get to the marina that hauls it out for the winter. Upon  
arriving, the mechanic checked the batteries and determined that they  
were fully charged and did not have any dead cells. I turned the  
battery switch to "off" and had all of the circuit breakers on the  
panel off as well. The bilge pump is not hard wired to the batteries.  
I returned 3 days later and found the batteries had some juice but if  
the engine did not start immediately, there was not enough juice to  
try to start the engine a second or third time. I then connected the  
shore power cord and it would not start the engine. Several hours  
later with the shore power cord still connected, there was enough  
juice to turn the engine over just twice.

Could something be drawing down the batteries even though all of the  
breakers are off?  Are the batteries bad after 4 years because they  
cannot maintain a full charge for 3 days? Your thoughts and help are  
appreciated. Thank you.

Joe Aberdale
#908