# Marine stereo wiring help



## wchevron (Oct 19, 2007)

i just bought a stereo for my boat. looking at the wiring diagram i am a little confused. i couldn't get the diagram to scan legibly but this is what is says:

blue wire: remote turn on. connect to amplifier or power antenna.

black: ground. connect to ground.

red: accessory. connect to existing ignition circuit or switched 12v source.

yellow: memory. connect to battery circuit or constant 12 v source

the rest of the wires are just for the speakers.

blue i don't need
black goes to ground, i get that.
red would go to the stereo breaker on the elec. panel.
yellow, would that go back to the dc negative bus bar? this is where i'm getting confused.


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## alecs123 (Jul 25, 2007)

you need the yellow wire to "keep alive" the stereo in order to keep your clock, memories and perhaps other sound settings.
It will draw a little current from your battery and should be wired to the + terminal.
If you don't need the clock to be on time and don't mind manually tunning your stations I would skip it


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## T37SOLARE (Feb 1, 2008)

> should be wired to the + terminal


Just make SURE you have an inline fuse on it.


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## wchevron (Oct 19, 2007)

how does it work with no negative wire? i thought you always need positive and a negative. thanks for the info on the yellow wire.


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## timebandit (Sep 18, 2002)

black wire


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## alecs123 (Jul 25, 2007)

the black is ground or negative. in a typical 12v dc circuit ground and negative is the same. For a boat there is a slight difference and it depends on your electrical circuit. Most boats with an inboard motor are "grounded" to the engine block and other fixtures, like through hulls, are connected to a "ground" (keel, or zincs) to prevent galvanic corrsion, this commond gorund is also wired to the negative pole on the battery.
For your simple installation, you can either use the ground, as described above, or simply wire your stereo to the negavite (-) wire/pole of your battery.


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## scottyt (Jul 19, 2008)

also you might want to think about hooking the yellow wire to a another breaker or small switch. so when you are one the boat you dont loose settings but when you park it for a while you can shut it off to avoid the small drain the memory functions take. 
you could also do this by hooking it to the battery switch, when the battery switch is on the yellow has power, when off it does not. that way when on the boat and the battery switch is on it keeps the settings


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## wchevron (Oct 19, 2007)

thanks for the help everyone. i'm assuming i can just connect the black wire/ground to the neg. bus bar.


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## alecs123 (Jul 25, 2007)

wchevron said:


> thanks for the help everyone. i'm assuming i can just connect the black wire/ground to the neg. bus bar.


that is correct


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## TSOJOURNER (Dec 16, 1999)

*S&S on Lake Anadaro*



alecs123 said:


> that is correct


Hello - I found some photos from about 2003 of the Dennis Connor wing sail Stars and Stripes yacht, on Lake Andaro. I see that you list Valle Bravo as your location.

Do you know anything about where it went after that, or what has happened to it? Can she still sail? Has she been completely destroyed, or do parts remain from her? Or someone else who may know anything?

Thank you very much for anything you can tell me about this boat's condition, or maybe about people who I can ask for more information.

Cheers!


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## TSOJOURNER (Dec 16, 1999)

*re: S&S on Lake Avandaro*



Stingrayj said:


> Hello - I found some photos from about 2003 of the Dennis Connor wing sail Stars and Stripes yacht, on Lake Avandaro. I see that you list Valle Bravo as your location.
> 
> Do you know anything about where it went after that, or what has happened to it? Can she still sail? Has she been completely destroyed, or do parts remain from her? Or someone else who may know anything?
> 
> ...


Corrected 'Avandaro' above.

It was owned at one time by a Victor Tapia, if that rings a bell?

From Wiki, 
_After the 32nd America's Cup, the hard sail yacht was bought by Mexican yachtsman Victor Tapia and sails in Mexico._


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## michaelmrc (Oct 30, 2008)

wchevron if your stereo has any digital settings ie bass treble radio presets etc.. you will need to connect the yellow wire to a full time source. red to a switched positive and black to your negative bus.


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## patrickrea (Aug 20, 2007)

Be advised that some stereaos won"t power up if the yellow "memory power" wire is not alive. In that case just connect it to the same main power source as the red wire.


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## tap (Apr 1, 2009)

I know this an old thread, but it shows up on the first page of google results for "boat stereo wiring", and if I found it, then is stands to reason that others will find it too.

I got a new stereo and measured its power draw. It's a Milennia MR380, but I imaging most are similar.

The yellow memory power, when the red wire is *not* connected, draws 720 µA. That's over 57 days to use one AHr, or about 6.3 AHr per year. So there's really no reason to worry about draining your battery with the memory power. Even a little 60 AHr battery would be drained just 10% after an entire year of being left connected. The battery's self-discharge rate is going to be more than that.

Once the red wire is connected, the power draw increases to 15.3 mA. That is with the stereo still off. That's 2.7 days for one AHr or a little over 11 AHr per month. No big deal if the battery is on a charger but significant if a smallish battery is going be left alone for months.

With the stereo on, but with no CD in the drive and the volume muted, power draw increases to 490 mA. That's a little over 11 AHr per day.

Turn the volume up and the power climbs. Playing from the SD card at max volume with two 4Ω speakers was around 2.8 A.

Interestingly, all the power draw is on the yellow memory power cable. I.e., when the radio is on and drawing 490 mA, the yellow wire has about 488 mA on it and there's around 2 mA on the red wire. So when your placing fuses/breakers and deciding what gauge of wire to use, the yellow wire is the one that needs to thicker wire and the fuse/breaker that won't trip for normal loads. The red wire is just a switch and can use thin "signal" wire and a low amp fuse.

Off: 6 AHr per year
Standby: 11 AHr per month
On not playing: 11 AHr per day


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## jbondy (Mar 28, 2001)

That is interesting that the power is mostly drawn thru the yellow "memory" wire. As Patrick stated above, "some stereaos (sic) won"t power up if the yellow "memory power" wire is not alive". Clearly that would be the case with yours. If there are some that will power up with the memory wire not connected, then for those, most of the power must be drawn thru the red wire. Either way, follow the manufacturer's installation instructions. And always fuse every power line.

I would never connect anything directly to the battery, with the possible exception of a bilge pump, because I want to be able to switch things off. And certainly the stereo, unlike the bilge pump, would be something that should be off when the main switch is off. Things that I want to be on when the main switch is off I wire to the hot side of the main switch. That is currently (pardon the expression) limited to the bilge pump and the yellow "memory" for the stereo. I put a small switch behind the stereo in the memory wire that I turn off when Pokey is put up for the winter, otherwise it is left on.

Also, an earlier post suggested connecting the black wire to the ground bus. If you have a battery monitor such as a Heart Link, battery use is accomplished by measuring the current that is returned to the battery bank from all circuits. A shunt is inserted into the circuit. Pokey's PO inadvertently bypassed this by wiring some grounds on the wrong side of the shunt. Just something to keep in mind.


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## QuickMick (Oct 15, 2009)

IIRC i hooked the yellow and red together then ran a sgl line to batt, my stereo has a built in fuse.


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## eherlihy (Jan 2, 2007)

...and you can listen to the radio regardless of the position of the battery switch or breaker...


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## Noelex (Jan 23, 2008)

tap said:


> I know this an old thread, but it shows up on the first page of google results for "boat stereo wiring", and if I found it, then is stands to reason that others will find it too.
> 
> I got a new stereo and measured its power draw. It's a Milennia MR380, but I imaging most are similar.
> 
> ...


I have measured the power consumption of a few CD /MP3 players and there is a great deal of variation between units.
If low power consumption is important I suggest you measure the power consumption of your player. Some require very little power to maintain their memory others consume much more.
A switch to turn this off or on is often useful.


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## Noelex (Jan 23, 2008)

tap said:


> Turn the volume up and the power climbs. Playing from the SD card at max volume with two 4Ω speakers was around 2.8 A.


That's high for a unit without a CD changer playing an MP3. Some units are half of this figure.
There is a big variation, the display on some units can consume a lot of power.
Maybe go shopping with a clamp on multimeter ! The salesman will be convinced your mad. 
Tell him you are concerned about global warming!


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## tap (Apr 1, 2009)

I don't think the built in fuse on a radio is enough to protect the wire. 

As I understand the ABYC requirements, you need to have a fuse/breaker with in 7" of wire from your battery. This fuse protects the cable leading from the battery to the rest of the boat, until they reach another fuse or breaker, at which that one "takes over" the protection. The fuse must be rated under the ampacity of the wire. I.e., the fuse most blow before the wire carries enough current to melt the insulation and start a fire. The wire between the fuse and battery (the 7") is unprotected. If there a short in that part of the wire, there is no fuse to blow, and wire will melt (unless it's very heavy gauge, in which case the battery might explode first).

Suppose the yellow and black wire touched outside the stereo. While you're connecting or unconnecting it or maybe one of the ring terminals falls off or breaks. The stereo's fuse isn't in that circuit and the yellow wire goes straight to the battery so you've got a dead short. The wires will melt.

Connecting the yellow wire to the other side of your battery fuse/breaker won't work either. That fuse is probably quite large, 50A, 100A, or more. All your boat's power runs through it so it needs to be big, and the wires it's protecting are the heavy battery to main panel cables that can take a lot of power before they melt. But did you connect the yellow wire with 4/0 wire? Probably not. Maybe 14 gauge, which has an ampacity of 35A (or less). 

So if you used 14 ga for the yellow wire, it needs a fuse of 35A or less within 7" of your battery. Thus, the inline fuse.


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## tap (Apr 1, 2009)

noelex77 said:


> That's high for a unit without a CD changer playing an MP3. Some units are half of this figure.
> There is a big variation, the display on some units can consume a lot of power.
> Maybe go shopping with a clamp on multimeter ! The salesman will be convinced your mad.
> Tell him you are concerned about global warming!


With the volume up, most of the power is going to the speakers. Sound is power after all. If the stereo's amp is rated for 20 watts power output, it's going to take at least 20 watts input to produce it.

Mine's rated 45W peak, 20W average per channel for four channels. Which seems pretty typical of a decent stereo. West marine's cheapest ($70) stereo package is only rated for 5W per channel. The next one up is 17W RMS per channel.

It seems mine uses 6W just to get the display on a play an mp3 with the volume muted. At max volume with two speakers it should be able to put out 40W of power, but I saw an increase of 29W. Maybe I need to play something louder? Or maybe the specs are inflated?

Anyway, how much power a stereo uses in operation is going to be primarily determined by how loud it is. More volume takes more power. The "better" the stereo the more power it can output. The stereo with the least power at max volume is probably going to be the cheapest one you can find, coupled with speakers with the highest impedance. Of course it won't be very loud....


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## Noelex (Jan 23, 2008)

tap said:


> With the volume up, most of the power is going to the speakers. Sound is power after all. If the stereo's amp is rated for 20 watts power output, it's going to take at least 20 watts input to produce it.


People get very confused about sound and power. Our hearing is logarithmic. When you are listening to even loud music the average level will be something like 1W.At 1w speakers will be producing about 90DB (which is loud) During the brief peaks the sound will be much louder somewhere around 100w, and periods when only a hundredth of a Watt is used
As the average is only around 1w per channel if we had perfect conversion we could produce this power consuming only 2w from the boat. Of course we don't have perfect conversion and have to drive other electronics to decode the music etc.
So no unless you are listening to test tones 
If the stereo's amp is rated for 20 watts power output, it's NOT going to take at least 20 watts input to produce music out of it at full volume.


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## tap (Apr 1, 2009)

Speakers are just very inefficient at turning electricity into sound power that reaches your ear.

A speaker might be rated with a sensitivity of 90dB/1W/1m, which means one watt of input will produce 90dB. But 90dB SWL, while loud, is only 0.001 watts. So the speaker needs 1000 times the power coming in as you hear coming out.

As you say, sound is logarithmic, so in order to get more decibels than 90 it will require a lot more power. While 90 dB is loud in a quiet room, add an outboard at 100+ dB and try to listen to cabin speakers in the cockpit, and then you might want a little more. If 1 watt in gives us 90dB out, then 20W in will give us 103 dB. Getting to 110 dB will require 100W of power.

So an amp rated at 20W RMS power output really does dissipate an average of 20W to the speakers (and the speaker wires). To do that requires at least 20W of input. Of course only 0.02W will reach your ear, assuming it's on the speaker's axis one meter away.


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## Noelex (Jan 23, 2008)

tap said:


> Speakers are just very inefficient at turning electricity into sound power that reaches your ear.
> 
> A speaker might be rated with a sensitivity of 90dB/1W/1m, which means one watt of input will produce 90dB. But 90dB SWL, while loud, is only 0.001 watts. So the speaker needs 1000 times the power coming in as you hear coming out.
> 
> ...


100db is the loudness of a jackhammer at 3 feet. If you are listening to that as an average level I hope you are not anchored near me. 
Your 20w car stereo could not hope to produce this as an average sound level with music let alone 103db or 110dB. During the loud passages the amplifier would "Clip" which not only sounds dreadful it destroys speakers very quickly.


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## tap (Apr 1, 2009)

An outboard can be over 100 dB. If you're just as far from the OB as the speakers, doesn't it stand to reason that you'd want your music to be as loud as the engine?


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## Noelex (Jan 23, 2008)

tap said:


> An outboard can be over 100 dB. If you're just as far from the OB as the speakers, doesn't it stand to reason that you'd want your music to be as loud as the engine?


No one is a steady state noise the other is rapidly changing in volume.


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## tap (Apr 1, 2009)

Just which is the steady one?

I would think an outboard's sound output comes primary when the cylinders fire and would look like very large short pulses. On the other hand, modern recordings are heavily compressed with a limited dynamic range. In fact, I very much doubt any music recorded to a CD has the dynamic range of a real outboard.

But anyway, my points were:

Judging stereos by what uses the least power at full volume isn't useful. It's like buying an outboard that uses the least gas at full throttle. You're just going to get the smallest outboard that way. Now if you looked at what stereo used the least power while delivering 10W/channel to the speakers, akin to the outboard that uses the least gas while putting 10 HP to the prop, you'd have something.

100 dB SPL measured 1m from a speaker on axis is quite achievable without a power amp with a DC-DC converter. The speaker is very important here, as their sensitivity has a much greater range than stereos' amps power ratings do.

100 dB from a speaker isn't insanely loud. One foot from your ear, yeah that's pretty darn loud. Not that there aren't people who do such things... But stick them in the cabin, go to the cockpit and turn the outboard up full throttle and it won't seem that loud anymore.


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