alternator / batteries

[chrisarvor]

i have 2 batteries which start and run the electrics.
the boat has 220 hp mercruiser 1 year old .
i would like to add another battery would this be to much for the factory fitted alternator?

<hr width=100% size=1>

 

[paulrossall]

Depends what the output (in Amps) of the alternator is. I think the output of the alternator should be at least one tenth of the total battery capacity.(total amp hours of all batteries added together).
For example my alternator has an output of 55 amps and I have two 110 amp per hour domestic batteries and one 55 amp per hour starting battery giving a total of 275 amp per hour so my alt. output is adequate. IMHO.Paul

<hr width=100% size=1>" there is nothing-absolutely nothing-half so much worth doing as simply messing about in boats".