Wiring positive cable from Amps to battery or common on Switch?

Q

quirozjorge633

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Jun 13, 2025
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Hello everyone,
First off, this is my first boat so I'm new to a majority of this stuff, and I have done plenty of research on the topic and have seen so many different opinions on what the better option is which is why I am asking this question again.

The boat I own is a 2002 Reinell, 1 outboard motor only.
I have 2 batteries, (#1 starting and #2 deep cycle) as well as a perko switch (1, 2, both, or off). I took the boat to the stereo shop the other day to get rewired and they put the positive wires from the amps directly to battery #2 (deep cycle). There's are also fuses attached to the cables.

I have seen many people say the positive wires should go to the common switch, as well as others saying directly to the deep cycle battery.
I plan on starting the boat with #1 (starting battery), then switching to both when I go for a ride, and when parked listening to music I'll slap it on #2 (deep cycle).

With given information, is it better to leave as is (directly to battery) or disconnect the positive wires from battery and wire them to the "common" on the switch instead?

Any tips are always useful! Thanks. 😊
 
C

Chris1956

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Mar 25, 2004
Messages
28,214
They put the amplifier wires on the deep cycle battery so that it would not discharge the starting battery. You need to set the battery switch to the starting battery to avoid discharging the starting battery to the one powering your amplifiers.

Once the boat is running you can set the battery switch to both, to charge both batteries, when going to/from the dock.

That is only one way to power the amplifiers. There are others.....
 
Bondo

Bondo

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1 outboard motor only.
Click to expand...
Ayuh,...... Welcome Aboard,....... Do you plan to run a battery charger on the batteries when yer not boating,..??..??
As noted it won't matter how you hook up the amp, so long as you don't use both batteries when the motor isn't running, so it'll start when you want to leave,....
The reason for my post is, usually outboards have extremely weak charging systems,.... usually only a few amps per hour,.....
 
J

jlh3rd

Senior Chief Petty Officer
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Jul 10, 2017
Messages
686
I installed a master battery switch for all my dash switches. I also have a stereo switch downstream from the master battery.
How would you disconnect that amp?......as asked above.
I just have a simple pontoon, but running two batteries.

BTW, FWIW, and FYI...I have learned that you do not want to switch batteries while the motor is running. I have a 2021 Merc outboard and my understanding is that can fry the electronics for the charging system.
 
dingbat

dingbat

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Nov 20, 2001
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16,439
jlh3rd said:
I installed a master battery switch for all my dash switches. I also have a stereo switch downstream from the master battery.
How would you disconnect that amp?......as asked above.
Click to expand...
“Master” switch should shut everything off on the boat except bilge pumps which are wired direct to the battery
jlh3rd said:
BTW, FWIW, and FYI...I have learned that you do not want to switch batteries while the motor is running. I have a 2021 Merc outboard and my understanding is that can fry the electronics for the charging system.
Click to expand...
Not necessarily.
Most switches anymore are “make before brake” switches…the new connection is make before the old is terminated.
.
 
J

jlh3rd

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Messages
686
“Master” switch should shut everything off on the boat except bilge pumps which are wired direct to the battery"

It does....that's why I called it a master battery switch...don't have or need a bilge pump.

"Not necessarily.
Most switches anymore are “make before brake” switches…the new connection is make before the old is terminated."

The info either came from my motor manual or New Wire Marine or maybe"" Boating". Regardless, it was a legitimate source. My selector switch said nothing about being "make before break", nor did new wire or the package.
You can gamble with your $12,000 motor. I'm not.
The newbie can make his own choice.
 
Last edited:
C

Chris1956

Supreme Mariner
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Mar 25, 2004
Messages
28,214
Gee, Consider the following:

Outboards from 20+ years ago have hefty charging ability. my '93 Merc V6 charges 40A. My '98 Johnny V6 charges 35A. Newer motors often charge more than that, especially DFI types.

Fusing the amps properly will stop 'em from smoking. There is no need for a separate switch. I like a master disconnect for all accessories, but it can be a dashboard switch which is convenient.

The vast majority of battery switches from the last 20+ years are make before break. This protects the charging system.
 
nola mike

nola mike

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Apr 22, 2009
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Most (all?) amps that I've seen are turned on by the head unit anyway, so while there's battery power to the amp at all times, it isn't "on". I have my head unit on a switch, so unless the switch is on the head unit isn't getting power. If there were an acc position on my ignition switch I'd use that. Main amp with a direct fused wire to my single battery. Someone please explain how this would be inappropriate or let the smoke out
 
Q

quirozjorge633

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Jun 13, 2025
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Toyelectroman said:
I wired mine to the common post on my battery switch, not to say wiring directly to the battery is wrong.
Click to expand...
That is what I'm also hearing. I don't know what the main difference is, but personally I feel like leaving it wired directly to the deep cycle battery is better so I know for a fact that when I am parked and play music (leaving it on both or changing it to #2) I can still start the boat up and not have any chance at draining battery #1 if I forget to switch it from both to #2 when I park. I strictly want battery #1 ONLY for starting the boat and night lights so I'm not stranded somewhere.
 
Q

quirozjorge633

Recruit
Joined
Jun 13, 2025
Messages
3
Bondo said:
Ayuh,...... Welcome Aboard,....... Do you plan to run a battery charger on the batteries when yer not boating,..??..??
As noted it won't matter how you hook up the amp, so long as you don't use both batteries when the motor isn't running, so it'll start when you want to leave,....
The reason for my post is, usually outboards have extremely weak charging systems,.... usually only a few amps per hour,.....
Click to expand...
Yes I have a 2bank that I'll have connected to both batteries so I can start her right up the following morning or next time I take her out. But yes I agree, I think leaving it directly on batt#2 is the better idea so #1 will always be enough to start the motor.
 
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