18 V too high?

I am running a PPI-PCX2200 amp in mono mode so its pushing 800 watts. I have 2 batteries in my boat. The stock staring battery in the back of the boat and an optima blue top under the observer's seat with the sub and amp I have. Most of the time I run the boat with the stereo at a normal level, I read between 12.5 and 13.5 V on the my dash gague. When I pump up the tunes and get the sub really pounding, I drop down to 12 V. But yesterday when I took the boat out after filling sacks (about 30 min with the boat off) I got readings at 18V, even at idle and i heard my alternator whine. After a while it dropped back down to normal, but as soon as I turned the stereo on agian, it kept charging at 18 V agian. After a good hour, it went back to normal and was back to normal for the rest of the night. Should I be worried? Or was the battery just that low from filling sacks?

18 volts is way too high for a 12volt system. it should not run more than 15.5 volts or damage to battery and electrical circuits can occur especially if your boat has a computer contolled engine

18V is not low, it's way to high and will damage several systems on your boat (least important the battery itself). Are you sure the gauge was good? If so, check the voltage regulator.. It's not expensive but it needs to be good, don't go boarding if this is not correct (14,5V+ when running).

So, you're saying the computer is shot? Or could be?

Yes it can be...
Hopefully there is no damage done, and the motormanagement system is protected against this. But keep a second voltage meter in the boat, and when starting the boat next time measure the DC-Voltage of the battery.
Also when the battery is almost empty (when running the stereo or filling the fatsack), the alternator shouldn't be charging with more then 14.5V.
Keep a good look at the voltage gauge the next few times when boarding.

Good luck!

What do you think would be shooting the voltage this high? Should I disconnect my second battery, which has all my stereo stuff on it and see if that makes a difference?

How are the two batteries connected?

Rod

In parrell, how they are supposed to be. Positives to positives, negatives to negatives. It was working fine for a good month or so. It was just like this last time I was out. Alternator problem or what?

The only problem I could think of is; 1) The voltage regulator is about the end of his life (therefor the high voltage), or 2) a faulty gauge. I hope for you it's the latter, although the first one isn't a huge problem either.
Therefor take a good second voltage gauge with you the next couple of times going out and carefully check the voltage (at battery, altenator or starter). When you see 14,5V+ at your gauges, shut down the engine and take it to the dealer. The problem can be fixed within a hour and shouldn't be a huge problem if nothin is damaged.

If the batteries are connected in the way you say then it's correct and the battery voltage can never be above 15V+. And if it worked correct for a month it shouldn't a problem.

Check the boat without using the stereo, fatsacks, etc.. If this is correct, turn on every electrical option one by one and see what happens.

Well my uncle is my mechanic and he was the one who told me to not to put in the stereo at all. So, agianst his recomendation, I did. Is there an easy way to change out the voltage regulator? It is a 94 MC PS 205 with the 275 TPI Fuel Injected engine. I know it is not a faulty gague because I can hear the difference in the engine.

I can't imagin why he would recommend not installig a stereo other than he doesn't like your music!

As for the voltage regulator, if it is external then it should be easy to change. A lot of systems these days have the voltage regulator internal to the alternator and you can't really change it.

Look at the alternator: if it has only one large wire attached to it then it is certainly an internal regulator. If it has a small wire attached to it, follow that wire back, it probably goes to the voltage regulator.

Before I changed anything, however, I would get a reasonable multi-meter and check things out a bit more. When your dash meter is saying you are charging at 18 volts, get the multi-meter out and see what it says.

Measure directly on the batteries. I would be really, really surprised if the batteries had 18 volts on them and they would still work well enough to start the boat.

Measure the voltage at the large terminal on the alternator. If it is 14 volts or so then the gauge in the dash has gone crazy.

If it is reading 18 volts then follow the wire where it goes. If the voltage is 12 volts at the battery and 18 volts at the alternator then somewhere in between there is a problem.


Rod

Thanks rod, will do tomorrow! I'll keep you updated. He didn't want me putting in the stereo because of the load it would supposedly put on the whole electrocal system. Before when we would pound the sub, the voltage would drop down to 12V as opposed to 13V that is normal. Then is would shoot up to about 14V if the battery was real low. Then I put in a blue top in addition and it was fine. Never above 13.5 volts. I'm going to check everything tomorrow and go from there.

Rod Deserves Wakeworld Hall Of Fame status for helping people out with their boat electrical problems. A year ago he helped me diagnose and figure out a couple things about our electrical problems. Luckily ours was a simple Alternator (integral regulator) change after some high Voltage spikes and popping breakers.

I have a much better feel for the boats electrical and have no bones about running around the boat with a multimeter checking everything out. We now got tunes and a system that charges well. Good luck Mark and thanks Rod.

Flux, sounds like the same thing for me! I was looking to upgrade the alternator anyway. Can anyone tell me right off the bat if I have an internal or external voltage regulator.

Also, I think I have 4 awg wire running from the alternator to the battery and 4 awg from the main battery to the extra battery and 4 awg from the second battery to the amp. Do I need to upgrade?

I think you've got a internal regulator. But it easy to see on the alternator itself.

I would suggest to upgrade the 4awg from the main battery to the extra battery..

Hey Mark, we had only installed a head unit to drive our four speakers when all the stuff started going down. In retrospect, it was either a strange coincidence, or the head unit had a bit too much draw for the wire gauges feeding it. Recently, we put in a less powerful (and cheaper) head unit and have had no weird voltage stuff going on. The boat is a 92' Sport Nat and I know there is a short or two to some lights and things.

Here's a couple suggestions I have from info read from other posts on stereo's and boat electrical:

1. I am under the impression that you are running a head unit and an 800 watt mono sub amp, that probably puts your system in the neighborhood of 1000 Watts total, and can peak at 80 amps. That is alot. Undersized wiring may cause your regulator to fail as it cannot feed the demand of the system in amps, so it will boost up the voltage to try and compensate, then your breakers will pop. You may have damaged your regulator and may have to replace the alternator. I am gonna assume that you have an internal regulator as most do.

2. Isolate your second battery and put ALL your stereo stuff on that battery. People will recommend different isolators, but you can still get one under a 100 bucks that will work fine, with all the stereo stuff your got, you definately don't want it taxing your boats electrical system and/or draining your starter battery. You can search these posts, there is a ton of info on the subject. Run some power to your amps from the isolated battery with inline fuses.

3. Upgrade your wire gauges!! YOU GOT A 1000 Watts running on the system and for sure 4 gauge is not enough!! You may even want to consider a smaller amp for the sub, remember that it takes 4X the power to make a speaker 2X as loud.

4. Consider a HO alternator in combination with your isolated battery and big wire gauges. Your current alternator is probably in the neighborhood of 50 Amps, if you intend to add other amps for your regular speakers, you will be draining batteries quick if you are rocking out, or blasting some tower speakers.

Like I said, there are a ton of posts on this board about systems and problems and fixes, do a search and see what others have done. Unfortunately, it's a pricey affair, but taking short cuts get's you dead batteries and blown regulators. We actually downgraded our head unit to prevent mishaps, but we still got some tunes, nothing fancy, but it get's me going in the morning and keeps me relaxed all day floating in the lake.

I believe you can have your alternator tested to see if the regulator still works. Otherwise it may need replacing.

I was thinking of hard wiring my deck to the additional battery today anyway. Yes, I will admit, the amp is HUGE in comparison to what I need. I haven't been up there to test any of my ideas yet, but I will today. You think 4 gague is too small? I think im going to cut out the amp today and go from there. Also, it take 10X the power to make the speaker 2X as loud. It is an exponetial equation. I think I would be fine with a 50 watt amp for as much as I turn it down.

Thanks all! Keep the sugestions coming

You can look at amp wiring kits at any stereo store, they tell you the Watts they can handle. You can't oversize, only undersize.

Good luck Mark, I have fealt your pain and there is nothing more frustrating than trying to make your boat better only to find out you made it worse or not work correctly.

Please take my post with a grain of salt, I am going from memory and certainly don't want to give you bad info, Only some suggestions to give you some food for thought in trying to figure out your voltage spikes, they are bad. Usually these problems are hard to figure out, but easy to correct once you find it.

Well, I dropped the sub and amp this weekend and had no more voltage spikes. Im keeping my fingers crossed! Is there a chance that I did not really fry anything and by just elimating the HUGE amp, I fixed the problem. At least for now... Rob, whatcha think?