What kind of audio system can i support of an old mercury 50hp?

[CapPhil64]

I am restoring an old boat and want to set up a simple stereo and get the most sound i can out of my set up. I have a 76 Mercury 50hp. Only one battery at the moment. I have looked at stereo packages on ebay for $50 with speakers and stereo but i just found an amplifier that you can only hook an aux cord up to for $15. My worry is how much power i can pull from the motor. Any ideas or suggestions for what i should do?

 

[thumpar]

You can hook an aux cord to any amp. That is nothing special. Most outboards, especially older ones are only meant to keep the battery charged without a load. If it was me I would put in a second battery to run the sound that is separate from the engine battery system and charge it before you go out.

 

[CapPhil64]

Should i worry about hooking up the second battery to be charged by the motor so while i am not using the radio i can charge it off of the motor running? Or should i just go for a portable battery setup to charge off the boat?

 

[UncleWillie]

Keep in mind that the alternator is intended to recharge a battery that was used for 10 seconds to start the engine and then operate the engines ignition, a few nav lights and maybe a sonar while running.
That will leave less than 10 amps for other duties, and only while at more than half throttle.
If you will be operating the radio with the engine OFF, the largest alternator in the world will not help.
You can charge both batteries from the alternator, but remember that you will need to have the engine at half throttle or more for a few hours to do it.
A shore powered charger is often the only real option.

 

[64osby]

I run a second battery for my stereo, fish finder and a couple other misc things.

It is not connected to the other battery or the motor. I charge it a couple times a year and it has never been fully drained or failed to work.

I would not run a stereo or any other device that might drain the starting battery. Last thing you would want is to beach for a couple hours, listening to tunes and then find your motor won't start because of a low battery.

A second battery is also a nice back up in case your starting battery fails.

Some stereos also have a low battery warning feature.

 

[CapPhil64]

I think I will just go with the spare battery option. i have the perfect out of the way spot in the front under the seat. That sounds like it will work the best! Thanks for yalls input!!

 

[smokeonthewater]

I disagree.... a normal low power stereo (ie 15-25 watts rms per channel) draws very little current and you already HAVE a backup if you somehow manage to run it dead... a 50 hp outboard in good condition it easily pull started.... I could (barely) pull start my dad's 100 hp motor at the age of 12.

You should be able to play the radio without draining the battery at all while running the engine fast enough to charge the batt and it would probably take several days without running the engine to fully drain a decent size battery especially at reduced volume .....

 

[achris]

He ^^^^ got it right...

The output of the engine changer is around 9 amps. That's about 100 watts. If you run a 'normal' radio at 'normal' volume it will be putting out around the 20 watts mark (10W a side). Most marine batteries are around the 70 to 90 Amp/hr rating, which means you could run that radio for around a week without flattening the battery! In fact, the amount of power drawn by that sort of radio would probably be easily supplied by a solar panel!

Chris......

 

[64osby]

I have looked at stereo packages on ebay for $50 with speakers and stereo but i just found an amplifier that you can only hook an aux cord up to for $15.

Might want to know the amp / watt specs of the add on. Some amps can draw a lot of power.

 

[CapPhil64]

He ^^^^ got it right...

The output of the engine changer is around 9 amps. That's about 100 watts. If you run a 'normal' radio at 'normal' volume it will be putting out around the 20 watts mark (10W a side). Most marine batteries are around the 70 to 90 Amp/hr rating, which means you could run that radio for around a week without flattening the battery! In fact, the amount of power drawn by that sort of radio would probably be easily supplied by a solar panel!

Chris......

Thanks for the clarification on the battery wattage output. I think I am gonna go with the solar power i just got recamended that by a neighbor.

 

[UncleWillie]

... I think I am gonna go with the solar power. I just got recommended that by a neighbor.

Be sure to run the numbers before buying into solar power.

20watts is going to be about 2 square feet of solar panel.
You will need to add a voltage regulator as Its output will vary wildly depending on the brightness of the sun. (>18v)
These two item will cost about as much as a battery. ~$100.

To get the 20w output you are expecting, the panel will need to be mounted on the boat and pointed at the sun, Not straight up.
You will only get full output when pointed square at the Sun and the sky is Blue, not hazy, not overcast.
You may need to put out two anchors to keep the boat from swinging in the wind.
The radio may die completely every time a cloud passes over and it definitely will not work at night.

Solar has its place, Large Sailboats crossing the ocean might be one of them.
Operating a small radio on the local lake is better done with a battery.
A motorcycle, or lawn tractor battery would likely be sufficient.

 

[achris]

I was just using the solar panel as a reference to how much power the radio would draw, not suggesting you use one....

 

[CapPhil64]

What I was recommended to do is to use the solar panel to charge the battery just to give it more juice but not to necessarily run the radio. Does that sound reasonable? Get a trickle charger solar panel and hook it up to the battery that will be seperate from the radio

 

[achris]

If you want a trickle charger, use something electrically powered, not the sun. Too expensive for what they are. Something like a Projecta 1600 charger....

Chris......

 

[CapPhil64]

If you want a trickle charger, use something electrically powered, not the sun. Too expensive for what they are. Something like a Projecta 1600 charger....

Chris......

I have found multiple trickle chargers for under $20. That's not much above what a standard one would cost is it?

 

[CapPhil64]

Just looking for something to stretch my radio life on the water. I could easily spend 8 hours out just anchored and jammin.

 

[achris]

Just looking for something to stretch my radio life on the water. I could easily spend 8 hours out just anchored and jammin.

A normal radio at normal volume for 8 hours wouldn't even put a dent in a normal battery. And with a 50hp outboard, you have a starter rope that will start the engine without the need for a battery.... So, even if you flattened it completely out, you can still get home...

 

[achris]

I have found multiple trickle chargers for under $20. That's not much above what a standard one would cost is it?

Yeah, that website is an Australian shop. We get ripped off something shocking here...

 

[CapPhil64]

Thanks for the input! I will post pictures of my stereo project when I get started. Just finishing up the main interior of the boat right now.

 

[CapPhil64]

I recently acquired a gently used marine starting battery. Would I be able to use this to power my stereo and not cause any problems? I am still waiting for my receiver to be shipped from over seas so I haven't been able to see how it runs off of my temporary car battery. After I get that in I'll be very close to sittin on the lake listening to my oldies.