Dual batteries on an outboard?? please help

[eroth111]

I have a 197something mercury 850. Im putting in a small stereo unit this season and Im planning on setting up a second smaller battery to run the stereo off of since outboards do not provide much charging power and i don't want to drain the battery on the water. I was going to wire up a switch to switch back and forth to use the secondary when the boat is off and I'm using the radio and switch back to the main when i want to start and drive. I want to know if this is plausible and if it will work. or any ideas for better solutions. any help would be much appreciated.
Thanks!

 

[Silvertip]

Re: Dual batteries on an outboard?? please help

You don't need two batteries. Just one good one. But if you insist, this is how it's done. Simple, cheap, and it doesn't get more versatile. Every accessory on the boat gets connected to the COM termnial on the swtich.

 

[eroth111]

Re: Dual batteries on an outboard?? please help

You don't need two batteries. Just one good one. But if you insist, this is how it's done. Simple, cheap, and it doesn't get more versatile. Every accessory on the boat gets connected to the COM termnial on the swtich.

thanks very much. so you think if I have one good battery i can go out and safely run the radio for a few hours and still be able to start the boat to go home?

 

[inthedirtagain]

Re: Dual batteries on an outboard?? please help

If you've got a thumpin' system in your boat and only one battery, you bettery buy the biggest one you can and wire some type of visual aid or alarm that lets you know voltage drop. You don't want to be stuck with anything less than 11.3volts. A radio/CD player by itself will run several hours and not produce much of a drain. However, if you are pushing amps and sub (or two), that's a completely different story and you'll want a dedicated battery (or two) just for that stereo system. Your 850 is likely running the same 9A stator that my '86 90hp has. Its enough to keep a surface charge when doing multiple starts throughout the day, but not enough to keep up with the electrical demands of big stereos and other electric doo-dads.

I have a single battery in my boat with a CD/MP3 player. I haven't had it on the water but a few times since I've bought it in April, but I'm liking the tunes on board. I have yet to have my radio kill the battery to the point that it wouldn't start, save for a wire coming loose on my enrichner circuit. If your motor is usually easy to start, I wouldn't worry much about a simple radio and multiple batteries.

 

[Silvertip]

Re: Dual batteries on an outboard?? please help

To verify how much battery you need, turn the radio on in your car. A standard marine radio is about the same current draw. I'm betting you can run that radio for a day and your car will still start. Add an AMP and all bets are off.

 

[eroth111]

Re: Dual batteries on an outboard?? please help

yeah I'm only going to be running a simple stereo deck and two 50w speakers no amp and no sub along with a couple led lighting strips on occasion and thats about it for power draw. its only a 15 foot boat lol. So from what it sounds like i don't need to worry about a second battery?

 

[inthedirtagain]

Re: Dual batteries on an outboard?? please help

I've got a 6-speaker system in my boat being powered by a simple CD player and one battery. So far, no issues.