David,
Every electrical device has a set amount of current draw, measured in  
amp/hours. You can total that up, compare to the battery's out put and factor in 
 the charging capacity of the motor and hours run and come very close to  
answering your own question. If you find that the motor isn't making up the  
difference, you can add a solar panel or a shore charger. My R22 is plugged 
into  shore power whenever it's at the dock. My stereo is the biggest draw 
and I've  found that it will stop working at about 10.5 volts on the meter.
 
Rummy
 
 
In a message dated 7/4/2012 2:04:12 P.M. Eastern Daylight Time,  
chsyhkr at gmail.com writes:

We  purchased our boat last year with a dead battery and no motor.  We  
added
the Tohatsu Sailpro 6 hp which has an alternator.  We wired it  to a new
battery and off we go.  We motor a little here and there  depending on the
weather.  How much charge am I keeping on the battery  with a little
motoring?  I have a plug charger and plan on taking the  battery out in
winter to store and charge back up.  I have also read  do not let the
battery get past half it's capacity?  I am no  electrician here............

I have read get a volt meter and as long  as you have 12-13 volts you are in
good shape.  We only run  instruments, lights, a radio, cell charger, small
fan, and water  pump.

Thoughts?

-- 
Regards,

David B.  Craft
Greensboro,  NC

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