The book is a good suggestion, but I'm curious, how much output do you get from
the alternator of a 5 hp engine? I know that some 9.9 engines have a 12 Amp
alternator, but you don't get that unless you're running hard. Also, you have
to consider how often you'll run the engine, and for how long, etc. For
instance, if you have to power for a while to get out of a river, you may
generate enough to provide for a day's usage. And if you use it every week, not
much will lost to self discharge.

On the other hand, if you don't use it often, a small solar panel might be
better.

Also, an AGM battery will have a lot less "self-discharge" and is easier to deal
with on a small boat.



"Jim Thompson" wrote in message
...
I am refitting a 17' Siren sailboat that has a 5 HP outboard motor. I
plan to put a 12V deep cycle battery aboard for VHF, sounder, lights,
etc. Can anyone point me to any do it yourself websites that discuss
this issue in particular?

I am interested in findiing out more about:
1. Battery size (~120 Ah should be more than enough).
2. Charging concepts (solar, outboard). Willl probably be leaving the
boat in the marina, and might not have shore power.
3. Battery monitoring. Since power requirements are low, I do not
want to spend a lot on expensive monitoring devices.

Jim