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Old 18-04-2009, 15:10   #1
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dinghy stereo help please.

I have a Boston Whaler Sport 130 that I use as a dinghy. This unit is powered by a 40 hp Mercury 4 stroke. According to the Mercury specs. this unit charges 18 amps. I realize that it only charges this amount at higher rpms. I am not sure how much it charges at idle or slightly above idle. I would really like to equip this boat with a stereo system, not a extremely high powered system but one that does sound good. I use this boat mostly for motoring around the marina and visiting other marinas in the area so most of the time I am idling around.

Does any one have any recommendations? The biggest problem would be the charging system. I would rather install a system than use a boom box portable. I am also really just looking to ad an amp and speakers and use my Ipod instead of buying a head unit.

Any input would be appreciated.
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Old 18-04-2009, 15:16   #2
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Well ... I have to say that if you DO put a stereo in your Whaler I hope you won't be motoring around MY marina as it's currently peaceful and quiet. Having to listen to someone else's music is hugely unpleasant. How about an ipod and earbuds so you aren't forcing your tastes on everyone around?
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Old 18-04-2009, 15:38   #3
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Well ... I have to say that if you DO put a stereo in your Whaler I hope you won't be motoring around MY marina as it's currently peaceful and quiet. Having to listen to someone else's music is hugely unpleasant. How about an ipod and earbuds so you aren't forcing your tastes on everyone around?
Roger that. It is quite unlikely that your musical taste is the same as mine. So why do you assume that I will be happy to listen to you music as you idle past?
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Old 18-04-2009, 16:11   #4
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Quite a friendly bunch here. As a fifty three year old boater here, all I can say is, you guys are quite assuming. I am happy to know that MY marina is much more friendly than this site.

Oh by the way, thanks for the constructive input.
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Old 18-04-2009, 16:52   #5
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Well, I cruised for years in a pocket cruiser with a 10 hp outboard that produced a maximum of 15 amps and I rarely ran it at more than 2/3 throttle. In addition to the stereo, I had running lights, gps, interior lights and many of the other electronic needs typical of cruising.

I'm don't pretend to be an expert, but I think here's a few of the issues you may run into:

1. Just because your alternator produces 18 amps, doesn't mean your battery gets charged at 18 amps. It can only accept so much. In addition, what it accepts varies depending on it's state of charge. I assume you have some regulation system in place.

2. Realize, the capacity of amps a battery holds is not a great indicator as to how many amps it will provide to run something. Many electronic components will not work once a battery is half discharged and I already mentioned some of the charging issues.

3. An issue you may run into with an Ipod dock is that it likely comes wired for 110, which means you will have to use an inverter. Again, I'm not an expert, but I understand every time you change like that you loose a lot of power to the conversion process.

Having wired a couple boats, my instinct would be to install a marine stereo/radio designed to run on 12-volts and withstand the marine environment. I'd play my ipod through one of the 12-volt plug options that allows one to play it through any FM radio. I do this on my boats and when chartering all the time. (I understand some stereos also come with an ipod plug in option.) I'd make sure my battery bank is the appropriate size to maximize charging efficiency and power output given my charging conditions.

My next choice would be to see if I can find a ipod dock that runs on 12volts and simply install a cigarette plug to run it on, removing it from the boat each use.

Another option is to purchase an Ipod player that has an internal battery with a long charge life. I have one that plays for 8 hours. It then has nothing to do with your dingy electric system.

Hopefully someone who is a bit more knowledgeable will expand upon this.

Best of luck with your project.
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Old 18-04-2009, 17:04   #6
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You probably have a 12V starting battery, you can run wires for a bus bar near where you will mount the stereo system run the system wires to it you can get a bus bar with fuses. You might want to install a cigarette lighter type 12V outlet as previously mentioned then you can run a spotlight or fan, your dinghy will be a real "tricked out ride". Don't run your battery down.

I'll take some Kingston Trio, Kassav, or Buena Vista Social Club.
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Old 18-04-2009, 17:07   #7
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I'd have to say that those responses were a touch brutal and I'd agree, assuming.

My response to your question is not very techy, but I have a little speaker thingy I bought for my wife a K-mart for her I-pod. I couldn't find anything I that put out any quality of sound until this thing. I says Surround Xi on it. About 2'dia x 8" long with speakers on both end that put out incredible sound. Paid $40 for it and went back and bought another one for myself. I later saw the same thing in Baharain for $16. I didn't catch any name on it, but the price diff jumped out at me.

it runs on AAA batterys or the 110 volt adapter says 6 volts-1 amp. I bought a DC voltage control from Radio Shack that I use for various things that are not 12 volt, so I run it on the house batterys.

It's not just a speaker. It has it's own controls for volume, pause, foward, back & reset. It needs the controls because in addition to a conventional input plug, it has a USB plug on it so you can put a flash drive on it and no need to carry anything else. Very small package, low power, incredible sound. I have in pluged into my Asus computer right now listening to a Canadian station on internet radio while I'm sitting in my slip in La Paz.

Life is hard.
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Old 18-04-2009, 19:20   #8
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First of all I would like to thank you for your responses. I must apologize for, perhaps, judging the first two responses too harshly. Again, my apologies.

My original thoughts were to purchase a system that I ran across from Poly Planer. It was designed for dinghies. The problem with it is, the price. I am not impressed with poly planer and for about the same price I could get a better quality marine amp and two better quality speakers from ebay. I was looking at a two channel amp that produced 80 watts per channel and a couple of 100 watt speakers. I would purchase an RCA cable that connects to my Ipod with a 3.5 mm plug to the RCA inputs on the amp. Part of the problem I face with the Boston Whaler is that the space between the hull and interior is injected with foam, really no space to install speakers mounted flush. I would really require marine box type speakers. My thoughts were to mount the amp under the bench seat along with the enclosed speakers. I really don't know of any quality enclosed speakers. The only ones that I have seen are the wakeboard tower speakers. Again, I only have room for a pair of 6.5" at most. These seem rather large for a boat this small. I can't find anything quality build smaller. I suppose the other problem is if I go too small with the speakers the system would definately lack bass. Like I said, I am not really looking to have an extremely loud system, just one that sounds nice. The fix for the lack of bass of the smaller speakers is a sub. That leads to a 4 channel amp with more power and more power draw. Installing a system like that would require at the least, another battery. You can see that one thing leads to another. There are miles of no wake zones that I will be traveling between lakes and marinas. My goal is not to disrupt the quiet marina settings but on the open lakes when I do throttle up I would like to hear the system. Your responses and ideas are appreciated. Does anyone know of smaller quality box type speakers? I guess I would rather have over kill and not have to turn the volume up than spend the money on something I won't like. If I did have to install a sub how small could it be? Again, I don't have room for anything like an 8" or 10" sub. I am not even sure they make anything smaller.
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Old 18-04-2009, 19:27   #9
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2007 Boston Whaler 130 Sport Power Boat For Sale - www.yachtworld.com

This link has some pictures of what my boat looks like. I may help.

Again, thanks for all your help.
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Old 18-04-2009, 21:37   #10
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I seems like you have a sound understanding of your needs and issues. I did have a couple box speakers as you described in one boat for similar reasons and was happy with them. I'm not sure about the brand but think they were the "higher end" poly planar reduced magnetic interference speakers. As I recall, they had a reasonable sound but I discovered any compass intereferance is too much, even if it is "reduced". Most people I've known who use non-marine stereo gear in marine environments to save money end up finding it was false economics. I should note I used them in a sailboat, not a fast dinghy so the wind/noise issues were very different.
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Old 19-04-2009, 01:36   #11
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First of all I would like to thank you for your responses. I must apologize for, perhaps, judging the first two responses too harshly. Again, my apologies.
No need to apologize. Our comments were snide; your response was sarcastic. That's fine; just the normal give and take that keeps this place lively.

Addressing your question more seriously -- this is just a question of electrical budget just like on the big boat. Amps going in need to match amps going out over whatever time horizon your battery bank gives you. So you should check the charging capacity of the outboard and the capacity of the starting battery and see what you've got to work with.

Personally, I think it's extreme overkill to put subwoofers and amps in a dinghy. If it were me (and it's not, so take with grain of salt) and I absolutely had to have sound in the dinghy, I would stick with a good marine-grade head unit and wire it directly to two enclosed waterproof speakers, and leave it at that. That should give you plenty of sound for this kind of occasional use, with the added benefit that the current draw is almost certainly something your existing charging system/starting battery can deal with. Less clutter, too.


We're sure that you're considerate enough to not be blasting quiet anchorages with the latest deth metal band at 120dB. Just in case, though, we have special sound-homing torpedoes prepared for such occasions, just so you know.
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Old 19-04-2009, 05:48   #12
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I am happy that we can put the initial posts behind us as "just the normal give and take that keeps this place lively."

That said, the only reason I am considering an amp instead of a head unit is simply because I am really only interested in using my Ipod. The AM/FM portion of the head is of little interest to me. I don't see a lot of sense spending $100 on a head unit that puts out 15 amps when I could spend the same $100 and get 80 amps. As for the overkill aspect, I would rather spend $500 or even $1000 on something that really sounds nice than waste $200 on something that disappoints me. It is my understanding that just because you have an amp that is capable of putting out 80 or 100 amps per channel the current draw that is put on the charging system and battery is relative to how high the amp is operated at. Full volume=full amperage draw. It is also my understanding that a higher powered amp system played a low volume will sound much better than a weaker tuner/amp played at the same volume. My understanding, although limited, is that the amp and speaker combination should be somewhat matched. In other words, it makes little sense to use a quality amp to push cheap speakers or conversely, an underpowered amp to push high end speakers. Just because a car will go 180 mph doesn't mean I have to drive it that fast to enjoy it.

I have spent a lot time researching but have yet to come up with an enclosed speaker system (marine grade) other than the wake tower speakers which tend to be large. Seems like someone would make something "in between".
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Old 19-04-2009, 07:41   #13
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Snook...with respect, I think you need some real help as a lot of your assumptions about amperage and watts indicate that you actually believe the specs you are reading. NOTHING could be further from the truth than car stereo specs!
You need several things to get want you want:
1. A dedicated battery and charger.
2. An inexpensive head unit with ipod input and LINE OUT jacks for an amplifier.
3. An amplifier from a quality manufacturer...and REAL specs from the back of the manual...not the box cover.
4. A pair of quality indoor/outdoor box speakers such as the Polk Atrium series or Boston Accoustics Voyagers.

You are correct that an amp will be required for satisfying sound levels. A basic car stereo will use roughly two amps of your battery power. You could listen to such a stereo for 10 hours and use 20 amphours of battery power. A legitimate 60 watt power amplifier going at rated power will draw 18amps + the amps of the radio...so 20 amps total and you would use that in ONE hour instead of 10!! This means that even with the motors running full tilt...you will be losing battery charge with your 18 amp alternator. A group 31 battery will provide 100amp hours of which you can use 50 before recharging. So...you could run your stereo with the engine off for only about 2.5 hours off a separate battery.
SO...you have some decisions to make. I suggest you read my more basic car stereo thread to give yourself a better grounding. Then you should decide whether you want the big sound so much that you are willing to install SEVERAL high capacity batteries and a shore charging system to give yourself the power reserves you will need for extended listening at high power.
I can recommend suitable products when you decide what your budget and power source will be. This was my profession a few years back and I am happy to help if you need it.
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Old 19-04-2009, 08:49   #14
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Fantastic post. I read your link. I have a couple of questions, if you don't mind.

1. I have read that I could just install an amp with RCA inputs and hook up a cable (RCA ends on one end and a 3.5 mm jack on the other end to hook up to my Ipod. Setting the Ipod volume control at high and adjusting the amp level to as loud and clear as I would ever listen to it, I could then just use the Ipod volume control to control the volume. True? I understand that this will not charge my Ipod.

2. Since this boat is open, without carpet, I will be hosing out the interior from time to time. The system(amp and box speakers) would be exposed (although mounted under the bench seat). Are the speakers you mentioned qualified for this use? This boat does have a console although rather small but enough space to mount a head unit if necessary. Since this console is mostly enclosed I would think that heat would be an issue should I mount the amp in it as well. I assume the amp would get much more air mounted under the seat. There is 55" X 10" of space under the front bench seat. I would like to keep everything mounted under the seat but off the floor.

3. I know battery/alt. output is a big issue. I could install a bigger and/or additional battery. I cannot find any information on the alt. output at different RPM's. For all I know the alt. output is 0 amps at idle and 18 at WOT. My guess is that is the case with at least some amps although limited in mid range RPM's. My question is, am I stuck with just a head unit, mediocre speakers and no additional amp as the battery/alt. remaining stock? What is the best system I could get away with at the stock battery/alt. that exists at present? Again, I could add an (1) additional battery but there just isn't space for a multitude of batteries. I do have a dock side charger at present.

4. Does it make any sense to install just a head unit, one with the highest amp rating by itself, and high end speakers such as the high watt speakers that are used by wakeboard boats? I have found a number of them in a 6.5" size that are two way speakers and have very waterproof enclosures. I would mount these facing rearward so I could hose the boat out from front to back. Some of these speakers have neoprene covers that could be installed prior to a wash down.

Like you said, my understanding of all of this is limited...just enough to get me into trouble, I suppose.

Sounds like you are just the person that would be extremely helpful to me.

I appreciated it greatly.
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Old 19-04-2009, 09:43   #15
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Fantastic post. I read your link. I have a couple of questions, if you don't mind.

1. I have read that I could just install an amp with RCA inputs and hook up a cable (RCA ends on one end and a 3.5 mm jack on the other end to hook up to my Ipod. Setting the Ipod volume control at high and adjusting the amp level to as loud and clear as I would ever listen to it, I could then just use the Ipod volume control to control the volume. True? I understand that this will not charge my Ipod.

2. Since this boat is open, without carpet, I will be hosing out the interior from time to time. The system(amp and box speakers) would be exposed (although mounted under the bench seat). Are the speakers you mentioned qualified for this use? This boat does have a console although rather small but enough space to mount a head unit if necessary. Since this console is mostly enclosed I would think that heat would be an issue should I mount the amp in it as well. I assume the amp would get much more air mounted under the seat. There is 55" X 10" of space under the front bench seat. I would like to keep everything mounted under the seat but off the floor.

3. I know battery/alt. output is a big issue. I could install a bigger and/or additional battery. I cannot find any information on the alt. output at different RPM's. For all I know the alt. output is 0 amps at idle and 18 at WOT. My guess is that is the case with at least some amps although limited in mid range RPM's. My question is, am I stuck with just a head unit, mediocre speakers and no additional amp as the battery/alt. remaining stock? What is the best system I could get away with at the stock battery/alt. that exists at present? Again, I could add an (1) additional battery but there just isn't space for a multitude of batteries. I do have a dock side charger at present.

4. Does it make any sense to install just a head unit, one with the highest amp rating by itself, and high end speakers such as the high watt speakers that are used by wakeboard boats? I have found a number of them in a 6.5" size that are two way speakers and have very waterproof enclosures. I would mount these facing rearward so I could hose the boat out from front to back. Some of these speakers have neoprene covers that could be installed prior to a wash down.

Like you said, my understanding of all of this is limited...just enough to get me into trouble, I suppose.

Sounds like you are just the person that would be extremely helpful to me.

I appreciated it greatly.
You're welcome!
Answers...
#1. YES you can do that but you will want to wire the amp to an on/off switch with a breaker rated slightly above the amplifiers' amp draw. You will want to run the IPOD at no more than 80% of full volume during set-up and adjust the amp volume on the Pot control just to the point where you begin to hear distortion in your speakers...then back it off a bit.

#2 Yes...the speakers I suggested will stand up to fresh water hose downs. If you go with a radio in the console there are no heat worries but any decent amp will need good airflow around it...though not necessarily a lot of space. Amplifiers...even marine ones...are NOT designed to get wet. You will need to design an enclosure that provides air flow but also protects the amp.

#3. It is unlikely that your outboard alternator can provide sufficient amps to run a decent power amp system. Further...your battery is likely a starting or dual purpose battery that is both SMALL in overall capacity and not designed for continuous deep discharge use. The alternator is really there to recharge the battery from starting...and to run your elctronics an nav. lights. It can probably handle a 2 amp car stereo load but not a whole lot more. Without knowing the group size and type battery you have now, I can't speculate on what you have the capacity to run and for how long. I can only make an intelligent guess and tell you that a modest high power amp will draw 15 amps (even without the radio) and you CANNOT run that off your present charging system with the motor running without gradually discharging the battery. The way to measure what your alternator actually puts out is to discharge the battery by running some stuff for a while, then start the engine and use a clamp on meter on your red battery cable to measure actual amp flow at various throttle settings.
I expect that you can run a standard "hi power" radio and speakers with no issues as the draw is similar to other instruments. Just don't try running everything at once with the motor on idle.

#4. The ONLY solution that will drive high volume CLEAR sound for you is a separate amplifier ... and it appears that battery capacity is your limiting factor..but you CAN leave the dock with a fully charged auxillary battery since you have dock side charging. If you take 15 amps as the current draw of an amplified system...then 30 amphours in battery capacity gives you one hour of listening. So...a group 31 gives you 100amphours divided by 30....a group 4D gives you around 180amp hours divided by 30...and an 8D would give you 250 amphours/30....depends on the room you have.
With the engines off...even with an amp you are probably gonna turn the volume WAY down to levels achievable with a standard car stereo and this means your amp draw will go way down as well...probably in the 3-4 amp range at reasonaby loud levels. So...the question for you is what will be your mix of engine off and engine on listening and how much extra battery capacity will meet your needs. Hopefully the amp hour capacities I have provided you will help you decide that.
If you decide to get a "hi powered" radio without an amplifier it will give you plenty of volume with the motor off...not enough to keep you happy with the motor on...and LONG hours of listening with even a group 31 auxillary battery.
I see NO advantage in getting wakeboard type speakers over the box speakers discussed earlier as the sound quality will not be as good and you are paying a lot for things other than sound quality which you do not need. The Atriums and Voyagers (among others) are deigned to take all the weather you can throw at them. If you had lazarettes, a good 6.5' coax flush mount would be a good choice, but with a Whaler, that is not possible.
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