Enough charging for radio?

I have a 1977 Mercury 850 (85 hp) outboard on my boat and was wondering if it will supply enough charge to the battery to run a 200 watt stereo. Will it be able to keep up or will I have a dead battery at the end of the day?

Anyone?

Re: Enough charging for radio?

How many hours do you run your motor and at what RPM and how many hours do you run your stereo and how loud?

Re: Enough charging for radio?

It depends, the least 2hrs and the most in a day of tubing and waterskiing probably 5-6 hrs. The average RPM is probably about 3-4.

The stereo will most likely be on all the time while on the water, not screamin' loud.

Re: Enough charging for radio?

Probably just measure the stereo's current at the volume you play it at and then figure what you motor can output for two hours and you will have the delta charge.

Let's say for example you can charge 2 hours at 10A and the radio takes 5 amps for 8 hours. The difference will be 20Ahours. Your battery will survive that. Just be aware, you would then need to charge when you got home.

Re: Enough charging for radio?

I'm sorry, I have never done that kind of electrical testing so not sure how to do what you are suggesting. Also, what is a delta charge?

Thanks

Re: Enough charging for radio?

Sorry, I meant the difference between the draw on the battery and the charge put back in.

You can buy multi-meters pretty cheap that can measure current and most can measure up to 10A. You would just pull the fuse and put the meter across where the fuse goes. You would turn on the radio at low volume at look at your meter. Then you would slowly turn up the volume while making sure the meter didn't go over 10A.

Re: Enough charging for radio?

Ok I think I know what you mean now.

Re: Enough charging for radio?

Think of your battery as a bucket and you are draining and filling at the same time but at different rates and over different times.

Re: Enough charging for radio?

Would it be wise to put a 2nd battery in?

Re: Enough charging for radio?

Read the instructions for your meter carefully. Many meters cannot handle 10 amps "continuously". The instructions will tell you how long it can carry that amount of current.

Re: Enough charging for radio?

::: bump :::

I'm interested in this as well.

I have same 1977 Merc 850 motor and would like to put a set of the Bose 131 Marine speakers under the consoles with the most economical headunit.

I have considered a second battery that would probably be deep cycle. I would be running the boat up river about 9 miles, fast and slow, some skiing. Then stopping to swim usually for 1-4 hours. Then fast 90% of the way back usually 4-5krpm.

Re: Enough charging for radio?

I plan to put a rather large stereo (way more than yours) in my boat and will be charging it from an outboard motor as well. I have been building custom audio systems professionally for 6 years now. A 2nd battery is always a good idea, I plan to run the best batteries I can afford and isolate them so when the motor is not running the stereo cannot drain my starting battery. I am also going to install an on board charger/maintainer so when I get home I can plug it in and let it charge till next time I take the boat out. This should also extend the overall life of the batteries.

If you are running a true 200 watts (most amps are overrated) just to give you a ballpark figure at full tilt the amplifier alone,whether external or built into the radio, should draw roughly 20 amps. That does not include any other powered audio equipment or accessories like depth finders gauges lights etc that your boat may be equipped with. I have no Idea what your motor (or mine) is capable of charging at but I would assume it won't be able to keep up on its own.

What I recommend is start by adding a 2nd battery, would be best if it was isolated from the starting battery but not necessary you will just need to watch the voltage to make sure you won't get stranded. Also a charger or at least charge your batteries after a day on the lake. Outboard motors and their charging systems were never designed to run high current equipment like big stereos so any help you can give the charging system is a good idea.

Re: Enough charging for radio?

I would strongly suggest you 850 folks find out two things: what is the amp draw of the tunes equipment, and what is the amp output (and required RPM to do so) of the motor. I think you'll find the the motor output to be pretty anemic ...

Re: Enough charging for radio?

so what is the best solution. I too have a mercury 75 o.b. engine and a substantial "tunes" load. I did have two deep cycles paralelled but after a summer burnt the voltage regulator up. This year Im running just one deep cycle and the same audio equip on a new voltage regulator. I have just had to repair wiring tonight on the new regulator. several connections got hot. What the heck. Do I have to carry enough spare batteries to run music for the whole weekend or will this engine handle it. ????? help

Re: Enough charging for radio?

outsider is right all you guys should find out what kind of output (in amps) your getting. Like we both said the output is probably not that much, they were only designed to keep a battery charged up for starting and maybe some lights etc.

Honestly I doubt your motors will be able to keep up with any decent amount of draw a stereo will have, so I think the best thing to do is get a battery with a good reserve to run your stereo and only rely on the motors output to give it a minimal recharge then put a charger on the battery when you get back home or back to the dock at the end of the day. This is another area inboards are good for cause they run alternators not stators big difference

I would think a simple radio and 2 speakers at moderate volume would be ok (not perfect but ok) but anything more than that your talking some serious current draw compared to a boat with out a big tune box.

as an example In my last truck I had 2 BIG stereo batteries that were capable of some serious output (about 1500 amps each in small bursts) these batteries retail for about $400 a piece and I could run my 3000 watt stereo at full volume for roughly an hour without the truck running before I had to worry about voltage issues, your boats won't be anywhere near that but you get the idea that amplifiers and such like to use up power.

zforsyth: sound to me like you are overloading your charging system causing the wires to get hot and eventually will burn up your new regulator. How big of a stereo are you running in your boat?