sizing a stereo system for a small boat

jcole59946

Cadet
Joined
Sep 27, 2009
Messages
28
My boat has one 70 amp alternator and a single battery

One Interstate 24M-XHD battery with 1000 cold cranking amps and a 135 minute reserve.

Is there a mathmatical formula that can be used to size a stereo system for this boat?

Could the system be set up to run full power when the motor is running and disconnect some speakers and amps when the motor is off?

In short, I want the biggest system I can run that won't leave me stranded.

Assumption 1: any amps would be class D digital
Assumption 2: the boat is mostly used during warm weather
Assumption 3: the battery is kept in good shape
Assumption 4: The boat has minimal lights and accessories
 

Grandad

Lieutenant Commander
Joined
Jun 7, 2011
Messages
1,504
Hi j. I must be getting old, but I have to say it. I've never been able to figure out why a "big" stereo system is needed when you're out on the quiet water, within a few feet of the speakers. But then I've never understood those stereo powered Honda Civics either. I guess my moniker says it all. - Grandad
 

NYBo

Admiral
Joined
Oct 23, 2008
Messages
7,107
There isn't enough information to answer your question. For example, how much time would you be running the motor and how much time running on battery? At what charge level will the motor no longer start?

Simple answer: Add one or more batteries dedicated to the stereo. Use an automatic charge relay (ACR) to help charge it/them.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
To avoid personal insults from angry property owners and other boaters I would suggest you install the smallest stereo that you can hear from about five feet away. I'm with Grandad on this. Sound carries so far over water it can be really annoying. But no -- there is no formula other than adding up the maximum current draw of everything on the boat. That's the amount of current being drawn from the battery if everything was on at the same time. Next you need to determine if your engine is properly tuned and if the charging system is working properly. If you repeatedly have to crank the engine to get it fired, then something is wrong and that cranking sucks a considerable amount of juice from the battery. Maximum alternator output is not achieved at low speed so you can throw that number out the window. The very minute you add an external amplifier you put yourself in a two battery system (unless you like to paddle or hailing passing boats). So the point of all this is that there are many variables to consider. We don't know what yours are.
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,657
A bluetooth mp3 player and 4 sets of wireless headphones works for me.

I use an old iPod plugged into a base for the wireless phones.
 
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