Batteries not charging problems

[tucker0104]

I am having a problem with my batteries not charging. I charged them the beginning of the season in early May. I have one new battery and one older battery connected through a 1/2/All/Off switch. I have an older Johnson 115hp outboard. I noticed my voltmeter going down slowly over the last two months. I am not running anything big. I have a stereo with two 6x9's and no amps. I am going to charge the batteries up today and see what happens. I am thinking one of the batteries might be bad, the generator on the motor is not running right, or something else. Any ideas what I should be looking for? Thanks for the help.

[MH Hawker]

Measure the voltage on the battery post them selves not at the connection points then start the motor and run the fast idle up to 2500 or so rpms , then retest the voltage, it should be higher with the motor running, if its the same then you have a charging problem.