How often should marine batteries be replaced?  I have had my boat for 3 1/2
years and don't know how old the batteries were when I bought it.  Can they
be tested or should I just think about replacing them this year?  I
certainly don't want to wait for a battery failure since my outboard is
electric start and I am installing an auto tiller this year as well.  Thanks
for any help.

Susan Crane
s/v Whimsy
Bohemia River
Chesapeake Bay