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Newbie Electrical Questions

Old 12-02-2003, 10:33 AM
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I bought my first boat last month and need some rudimentary electrical education. My boat is a 98 Parker 1800 with a 115 Johnson FICHT, SH Quest, Garmin GPSMap 168 Sounder and dual battery set up with a four position switch.

Now for my questions (laugh if you must)
1- Although rigged for two batteries I bought this boat with only one installed. Should I install the second battery? Why? How so as not to blow me or the boat up?

2- The navigation lights were not working so I had the shop look at it and they found it was due to a bad ground and fixed it. This sounds like the kind of thing that I could have figured out if I had the proper tools and reference materials. What would you guys suggest I pick up in order to cut back on boat yard labor?

3- The boat's volt meter reads 12v with the power off and pins itself with the power on. Not that I know but it sounds like a faulty meter to me. Is this something that I can swap out myself.

I am pretty handy but other than replacing light fixtures around the house, I have virtually no experience working with electronics. Any help or advice you could offer would be greatly appreciated.

Many thanks

Parker 1800 - 115 Johnson FICHT
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Old 12-02-2003, 11:25 AM
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Click here for battery discussion

The first thing I install on every boat I have ever owned is a dual engine battery setup. Call it peace of mind or whatever else, but this will prevent a call to SeaTow for a jump if you run your battery down.

You should get yourself a decent multi-meter. This will help you analyze electrical woes along with help from the awesome folks on this board. DC electrical problems will drive a man to drinking.



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Old 12-02-2003, 12:44 PM
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Sounds to me like you're already on generally the right track. None of its hard and DC power is real straight forward.

You do want two batterys in there, both of them the same size and type, and then wire the battery switch so that you may select between them to power the boat as well as start the engine. Then only use both in the even you have a battery to low to crank the engine alone. Alternate which battery you use by whatever scheme makes sense to you. The reason is that its cheap insurance against breakdown out in the water. The second reason is that it gives you the ability to run one of your batterys down if you find yourself needing to do that and stil having the security of a fully charged one to get you home.

If you're looking for background information and a general knowledge I have been told that The 12-Volt Bible for boaters is very good. I haven't read it myself but I've seen it for sale all over the place, even West Marine. So it might make for a good read.

That voltmeter should be reading zilch when the power is shut off and should generally be between the low 12.+ up to about 14.8 volts at the top end. Anything outside of those bounds and you may assume that there is a problem, and don't assume the problem is the guage. That assumption could get the boat burned down. I'd take it directly back to the dealer and have him deal with that one immediately. Most other stuff I could let slide, but not that one.

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Old 12-14-2003, 10:47 AM
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After reading the posts on battery types,setup and usage, it seems to me every method has someone recommending it. I'm also new to boating and the method I think I'll go with is 2 deep-cycle batteries, using only 1 and alternating each outing. Now, let's say after a few hours fishing(trolling), will it have enough juice to start my motor(yamaha 200 ox66) and approximately how long would it take running at cruise to fully charge the battery(35amp alternater output)?
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Old 12-14-2003, 12:18 PM
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I don't understand the question. If you're trolling then the engine is running. So why would you care about starting the engine?

Other than that, just do the math. See what the power use is for the equipment you'd be running, which may be suprisingly little, and then figure how much the engine is putting out. Figure at trolling speed the engine is only putting out 10 amps or so, far from its full 35, which it won't kick out until you hit about 2,000 rpm. So there may be a deficit and if there is that's the rate of draw on your batterys. If you've got typical Group 27 batterys figure them good for 100 amp hours capacity and you don't want to draw one down much more than about 2/3 of that if you intend to use it to also start an engine later.

Make sense?

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Old 12-14-2003, 02:15 PM
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Thom, I didn't quite ask the question properly. I meant in the case that I shut it down, would I be able to start up again with a battery at 60%. You answered my question fully though. Thanks.
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Old 12-14-2003, 02:33 PM
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Thomas was referring to "The 12 Volt Bibke For Boats" by Minor Brotherton. ISBN 0-07-156091-2

I got my copy at Barnes and Noble's, hobby section. If they don't have it in stock this info will help them (or any other bookstore) order it for you.
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Old 12-14-2003, 02:34 PM
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Just noticed that I said a vital part of that incorrectly.

You do not want to draw down your batterys to a state of charge any less than 2/3, and not even that much if you can help it. So if you've got 100 amp batterys that means take out no more than 40 amp/hours. Actually with many pieces of electronics you may find that they are shutting off on you at about 12 volts even and that's going to happen at about the 25% withdraw point.

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