Starting motor not charging

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brian62

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Jul 13, 2021
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I have an 1986 Lund with a 70 hp 2 stroke Mercury engine. My Pro Marine 5 amp single battery charger is not charging my starting battery but is charging my Trolling battery. Either it is in the motor or I have something hooked up wrong on the battery side. Before I put the boat away for the winter everything charged right. I checked the wiring and I cannot find the issue. I'm thinking the charger somehow goes through the throttle control then to the engine where it charges the battery, but I have no clue how to find the issue.

I could use some help since I am missing my fishing. :(
 

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KJM

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Doesn't your outboard charge up the starting battery? Maybe the battery is bad?
 
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brian62

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Battery is less than a yr old and I checked the wires to the battery to see if there was any voltage going to it and there was nothing. The charger is connected straight to the trolling motor and I think it is routed to the throttle control then to the engine then to the battery but I have no way of verifying this.
 
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KJM

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brian62 said:
Battery is less than a yr old and I checked the wires to the battery to see if there was any voltage going to it and there was nothing. The charger is connected straight to the trolling motor and I think it is routed to the throttle control then to the engine then to the battery but I have no way of verifying this.
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Turn the key to the on position and then see if the battery is getting voltage, that should tell you if the charger is routed thru the ignition. Can you jump start the engine from the trolling motor and then see if the engine is charging the starting battery? Also is there a battery switch involved here that could be in the wrong position? A new battery really shouldn't need a charger to start the motor everytime, maybe once in spring after all winter, mine don't even need that. Maybe some electrical device is left on that is draining battery?
 
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KJM

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With you nengine running check the voltage on the starting battery. It should read over 13 volts if the motor is charging it.
 
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KJM

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Also wouldn't hurt to clean all the battery connections. This should probably be the first thing to do.
 
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brian62

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I moved the switch to start position and the battery is not getting any charge.
KJM said:
Also wouldn't hurt to clean all the battery connections. This should probably be the first thing to
Click to expand...
 
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brian62

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I switched batteries and got the boat running. I verified there is no voltage coming to the battery.
 
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KJM

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brian62 said:
I verified the throttle control does not charge the battery in anyway or goes through it. It comes from the engine. Either it's the stator or the rectifier.
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Sounds like you are heading in the right direction!
 
roscoe

roscoe

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brian62 said:
The charger is connected straight to the trolling motor .
Click to expand...

Why is the charger connected to the trolling motor?

The charger should be connected to the trolling motor battery.

What is the voltage between the starting battery terminals when the engine is running?
 
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brian62

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The charger is connected the "trolling motor batter". ;)
When I used the trolling motor battery to get the engine started then removed the cables there was no voltage coming out of the cables. I verified the stator was good with 4.2 ohms which was perfect according to the manual. The rectifier didin't meet the specs so I ordered a new rectifier. Only thing left that could be bad for charging the starting battery. Only the stator and rectifier charge the battery.
 
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