Volt meter question

Aquatron

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I have a 1994 Aquatron with a Mercruiser 3.0. I?m in the middle of bringing it back to life; I put electrical power on it for the first time yesterday. When I connected my Battery for the first time my volt meter showed 12vdc, on my old boat and in the car you get nothing until you turn the ignition to on. I understand electrical theory and I understand voltage is felt and current flows. There seems to be nothing pulling any type of load so my question, is this just normal indication with the volt meter and the battery? I have a mercruiser book with wiring diagrams and I have just started to trace out the power path, I?m just hoping someone can save me some time and tell me this is normal operation??? Any insight would be much appreciated..
 

dingbat

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Re: Volt meter question

Voltage meters are typically connected thru the ignition switch. Sounds like someone wired it directly to the battery instead
 

JB

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Re: Volt meter question

Yes. And if left that way it will drain your battery.
 

Aquatron

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Re: Volt meter question

Thanks, that?s what I'm thinking. The little bit of looking around I did do yesterday made me a little nervous. I found a power wire coming off of the Trim pump going to a new fuse holder for the cigarette liter. That?s why until I ring out all the wires I will have a fire ext in my reach. If you don?t know what you are doing take it to someone that does?UGH
 

fucawi

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Re: Volt meter question

If the guy disconnected the battery when he was not using the boat then whats wrong with it going straight to the battery ? At least your readings will be more accurate . If its a digital dash meter they only draw 0.007 A ish ..so no problem .
fuses should be near the battery to be effective
 

Aquatron

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Re: Volt meter question

If the guy disconnected the battery when he was not using the boat then whats wrong with it going straight to the battery ? At least your readings will be more accurate . If its a digital dash meter they only draw 0.007 A ish ..so no problem .
fuses should be near the battery to be effective

Great point, and when I get sometime to crawl under the dash I'm going to look at the wiring. When I took a quick look i noticed a lot of factory wiring. Some of the shoddy wiring is prety clear to see, I'm wondering if this was a factory design. You make a great point on power draw the gauge is analog not sure of what type of power draw we would be looking at but it might be negligible. The one thing I did notice when I removed the positive post there was no spark like something was trying to pull a load.
 

fucawi

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Re: Volt meter question

A heated bi metal strip Voltmeter about 100 mA crossed coil about 20 mA ..disconnecting the battery is part of boating like filling the fuel tank or adding TWC3....so dont forget
 

Aquatron

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Re: Volt meter question

Thanks for the numbers. Yes you are correct, every time I put the boat up I disconnect the BATT. I use wing nuts for easy on and off.
 

j_martin

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Re: Volt meter question

Thanks for the numbers. Yes you are correct, every time I put the boat up I disconnect the BATT. I use wing nuts for easy on and off.

I turn off the key and the master power switch and walk away. Helps to have it wired right.
 

CaptainKickback

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Re: Volt meter question

Thanks for the numbers. Yes you are correct, every time I put the boat up I disconnect the BATT. I use wing nuts for easy on and off.

I don't know your boats setup, but disconnecting the battery and turning off the main battery switch are not necessarily the same thing. Depends upon wiring.
 

Aquatron

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Re: Volt meter question

I don't know your boats setup, but disconnecting the battery and turning off the main battery switch are not necessarily the same thing. Depends upon wiring.


Not sure what you are implying I never mentioned the main battery switch. I don?t even have a main battery switch, when I put the boat up I disconnect the battery. No mention of a main battery switch!!!
 

Aquatron

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Re: Volt meter question

My question on this thread was asking if anybody knew if this was a manufacturing wiring design. I understand how important it is to disconnect my battery when not in use. I was hoping someone had seen this type of volt meter set up. The boat manufacturer is no longer in business so I can't go back and ask them this same question that is why I came to this form. So please no more responses on how or why I need to disconnect my battery, or someone explaining the difference in a main battery switch and disconnecting my battery. The advice I received about the amp draw on the volt meter was GREAT help and that?s the kind of advice I?m looking for thanks. So back to my original question has anyone seen a volt meter hooked directly to the battery without going through the ignition switch? My suspicions? are that it is wired wrong but NOT sure just yet. I will look into rewiring if I feel the need, but having it read off the battery is not a bad thing.
 

Silvertip

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Re: Volt meter question

No -- it should not be wired that way. None of the other gauges are powered all the time and a voltmeter shouldn't be either. Move the +12 volt wire from it's current connection point to the +12 volt connection on any other gauge. It will then read battery voltage when the key is in the RUN position engine off, and charging voltage when the engine is running.
 

fucawi

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Re: Volt meter question

Quote
The advice I received about the amp draw on the volt meter was GREAT help and that?s the kind of advice I?m looking for thanks. So back to my original question has anyone seen a volt meter hooked directly to the battery without going through the ignition switch?

The problem is that many talking here have not embraced the modern technology or /and dont understand the implications of volt drops in the wiring ......
If its a digital meter you can leave it conncted 24/7 as the draw is so low. If you want an accurate reading with any meter you need two wires direct to the battery or direct to the main isolator switch so that current flows in the wiring dont change the reading. Any sort of meter can go direct to the battery if you turn off when the boat is not on the water.
If you want a meter switched by the igniton then you read not the actual reading but say " its reading what it normally does when everyting is OK " be that 13.5 or 14v or whatever ..it does not tell you the actual battery volts because of the varying volt drops in the cables..

Your boat do what you like ...your decision ..no saftey issues ..turn off when not in use and carry a fire extiguisher
 

Silvertip

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Re: Volt meter question

Gauges are almost always powered via the ignition switch. The ignition switch gets its power from a rather stout wire in the engine harness. The engine harness gets power from a buss at the engine via the very stout battery cable. Voltage drop at the switch and therefore at the gauges/voltmeter is negligible. In fact there is probably more error in the voltmeter than there is voltage drop. If the voltmeter at the helm is reading static 12.6 with the key off life is good. If it reads anything higher than 13.4 with th engine running life is also good. If It isn't -- don't leave the dock. If one really wanted to see what battery voltage is under all conditions, buy a "good one" and wire it through a relay located close to the battery. The ignition energizes the meter when the key is on and you eliminate any voltage drop. But once again, NO! Voltmeters are not typically wired that way and there is no reason to do so unless you want to. Besides, most electronics on the average boat are designed to operate on 11 - 16 volts so even a modest voltage drop will not be noticed by the operator or a cheap meter. High current draw items will obviously be impacted by any significant voltage drop. I recently had a discussion with a young man who was proud to have passed an auto electrical exam in his automobile repair program. When quizzed about voltage drop and what it means he had no idea what I was talking about as do a goodly number of folks following this thread.
 

bruceb58

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Re: Volt meter question

Wire it through the ignition switch. The voltage drops in the wiring are insignificant compared to the innacuracy of the voltage gauge itself. Its really just a "feel good" gauge anyway to tell you if your charging system is operating.

For those times you accurately need to know the voltages, buy a digital multimeter and use it.

To disconnect your battery, buy a switch and throw those wingnuts away and use some self locking nuts.
 

Lyle29464

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Re: Volt meter question

If you take it to a shop for work the mechanic is going to get side tracked finding out why part of your dash is on with out the key. I would just correct each problem as you discover them. The easy way is seldom the best way.
 

Aquatron

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Re: Volt meter question

FIXED!!!! Ok first thanks everyone for all the good ELECTRICAL advice and insight. I went out and I wired all my gages to go through the ignition switch and I also rewired the ignition switch itself. For some reason they had the Purple wirer going straight to Battery position but not anymore. I did notice one thing when I got the boat running the volt meter was reading 14 volts while running, I will keep an eye on this I?m still not ready for the water. This could be a result of the boat sitting for a while and the need to hit the battery hard. I wanted to say thanks again to all that had good sound electrical advice. I will definitely be using this site when I have issues there?s a lot of knowledge here.
 

fucawi

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Re: Volt meter question

14.4v at the battery is right on . 14v is toooooo low
 
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