Electrical grimlin - please help

[SmokyMtnGrady]

Hey Yall:
Last week we had some friends out on the boat and doing some water sports. I went to trim the motor down and the entire thing - everything including the motor shut off. I switched the battery to battery 2 and everything was fine.

I put a meter on the batteries when the motor was both on and off and the voltage on battery 1 was 12.9 volts and 13.1 on battery two with the motor off. I started the boat on battery 1 and the alternator at idle was putting out 14.1 volts on both sides.

Today we got caught in a long pouring rain so I cruised back to the marina on the lake at 7 knots in the rain at 1800 rpm. Then I noticed the voltage jumping all over the place between 12.1 and 15 volts on the boat's gauge. At the same time the Alpine stereo audio dropped out but the unit stayed on. I turned the boat completely off and it would not start on the battery 1 circuit. It started battery 2 and all voltage readings were normal and all the boat's electronics were fine.

I put her in the covered slip and I inspected the ground under the helm and it seemed very tight and is free of corrosion. I inspected the ground side of the battery itself and it too was tight and free of any corrosion.

I am going to look at the owners manual and see what else is wired into the battery 1 circuit and see where the ground is on the circuit as well.

Any and all ideas are welcome here as to what is happening here and the possible causes. I am stumped.

 

[seasick]

Hey Yall:
Last week we had some friends out on the boat and doing some water sports. I went to trim the motor down and the entire thing - everything including the motor shut off. I switched the battery to battery 2 and everything was fine.

I put a meter on the batteries when the motor was both on and off and the voltage on battery 1 was 12.9 volts and 13.1 on battery two with the motor off. I started the boat on battery 1 and the alternator at idle was putting out 14.1 volts on both sides.

Today we got caught in a long pouring rain so I cruised back to the marina on the lake at 7 knots in the rain at 1800 rpm. Then I noticed the voltage jumping all over the place between 12.1 and 15 volts on the boat's gauge. At the same time the Alpine stereo audio dropped out but the unit stayed on. I turned the boat completely off and it would not start on the battery 1 circuit. It started battery 2 and all voltage readings were normal and all the boat's electronics were fine.

I put her in the covered slip and I inspected the ground under the helm and it seemed very tight and is free of corrosion. I inspected the ground side of the battery itself and it too was tight and free of any corrosion.

I am going to look at the owners manual and see what else is wired into the battery 1 circuit and see where the ground is on the circuit as well.

Any and all ideas are welcome here as to what is happening here and the possible causes. I am stumped.

First place to look is for a bad/loose connection at the battery or the battery switch. Since one battery works fine and it seems that the battery with the issue has a decent charge, I suspect a bad connection. Although it is possible that the battery switch is bad, that is a much lower probability. Also check the common ground wire that bridges the two batteries together.
Your issue should be fairly easy to locate.

 

[Daman858]

Yep, sounds like a bad connection or your switch is bad on the #1 side. Clean the terminals and grease them up to prevent corrosion and see how that works.

 

[SmokyMtnGrady]

Thanks Guys! Will do that.

 

[92explorer]

Swap Battery leads and see if the issue remains on Battery 1. You could have a dead\shorted cell in that battery. It will measure the 12.x volts but the battery will not be able to supply a load\current draw. How old are they? I have a few older one that wont start my boats but will run my electric clay throwing machine and jugs pitching machine fine.

 

[SmokyMtnGrady]

I am using AGM batteries from West Marine (dekka), group 27. Battery 1 is new because I killed it over the winter when I left the switch in the on position and it got really cold this year like -5 F here in the Smoky Mountains. Battery 2 is 2 years old. It could be a shorted cell. I am going to check all the connection folks here mentioned tomorrow.

 

[SmokyMtnGrady]

Went and checked out the boat today. Turns out the Battery 1 leads were all loose. It looked to be a big brass nut or brass colored at least and I turned a wrench on it and tightened it up. No more freaky voltage jumps and what not.

I inspected all the major connections on the boat and made sure all was/is tight and clean. I should be good to go for a while. Thanks yall for the input and advice. It helped.