Yamaha F40A Owner's Manual page 172

cC
A poorly maintained battery will quickly
deteriorate.
1) Check the electrolyte level at least
once a month. Fill to the manufactur-
er's recommended level when neces-
sary.
Top-up only with distilled water (or
pure de-ionized water suitable to use
in batteries).
cC
Ordinary tap-water contains minerals
harmful to a battery, and should not be
used for topping-up.
2) Keep the battery always in a good
state of charge. Installing a voltmeter
will help you monitor your battery.
If you will not use the boat for a
month or more, remove the battery
from the boat and store it in a cool,
dark place.
Completely
before using it.
3) If the battery will be stored for longer
than a month, check the specific grav-
ity of the fluid at least once a month
and recharge the battery when it is
low.
4-32
GB
recharge the battery