mariner 45 HP (Classic 50) wont charge battery

sjoefl01

Seaman
Joined
Oct 17, 2012
Messages
69
I was fishing this morning and the motor was a little sluggish to crank. I though maybe I had been playing the radio too long so I drove really fast for about 10 miuntes to let the battery charge before I trailered it. When I got home to flush the engine it wouldn't crank. I hooked my battery charger up and the battery was taking a charge really fast. I stopped the charger at about 50 percent charge and cranked the engine. I let it run for about 10 minutes. I checked the voltage at 12.2V when I turned it off the voltrage was the same leading me to believe that the charging system was inoperative. When I hooked my standalone battery charger back up the battery was back to 10 percent.
It started raining so I am back in the house now. I thought I would see if you folks knew any tricks. I have no idea how the charging system works in this motor. It started raining before I could get the cowling off. (Luckily)
 

jbjennings

Captain
Joined
Jul 18, 2007
Messages
3,903
Re: mariner 45 HP (Classic 50) wont charge battery

I'm unsure how to help because I think you may have multiple problems.
#1. I don't like to put batteries that aren't fully charged on a motor. It will ruin stuff.
#2. If it's draining your battery 40% in 10 minutes, then you have a ground fault somewhere in the system.
#3. The rectifier will blow every time if you hook up the cables to a battery backward. It's easy to check a rectifier. Just check and make sure the current only goes one way from the yellow post to whatever. If the rectifier is blown it won't charge.
#4. Most likely the motor wouldn't really charge the battery much if it were brand new. The system really just maintains charge. That's why I don't like batteries that aren't fully charged---they overload the charging system besides providing low voltages which build up heat in electrical goodies. Therefore, at idle, you would likely not see much of a change in voltage between the battery by itself and the battery attached to a running motor. I'll bet if your charging system is working, you would only see a few tenths of a volt difference between battery alone, and battery voltage at fast idle.

I would go through the wiring system which are known to get bad on mercs over time (or all motors, for that matter), and make sure all the wires are in good shape, and all connections are cleaned. Then check the rectifier and if it's o.k. then I'd run it again and check for difference in battery voltage at slow and fast idle.
Good luck,
JBJ
 
M

Maxz695

Guest
Re: mariner 45 HP (Classic 50) wont charge battery

1 comon problem is corroded or loose battery teminals cables too on both the bat side and the engine side. I have to change mine almost every year. Before buying anything check all grounds terminals and connections as sometimes corrosion will build up and a connection may look ok but it,s not.
 
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