Alternator upgrade advice

   What do you mean by upgrading? Do you need more current?

Just guessing, but I bet Tony's looking for a bigger alternator to power the stereo's etc. If you don't find the answere here, you may check wakeworld.com, or planetnautique.com. There have been many posts there by guys putting massive stereos in the boats as to what alternators, etc. BKH

don't know that I would size the alt based upon the size of the amp. Seems odd that a 550 watt amp could draw 36 amps when it has a 20-25 amp fuse on it, wouldn't the fuse blow, yes it would. Most problems that people have with the electrical system when they add amps and stereo equipement is the way the wire it up. If you run power and ground leads directly to the battery then you really don't have an issue and if you do then add capacitor for when the load is needed. I'm not sure that a 10 SI or 12 SI alternator would be a direct replacement for a '88 ford engine. You could have issues with the mounting holes, bracket and pulleys. If memory serves me right the majority of them went out the door with multi-vee pulleys which don't work very well with single groove pulley's.

I love this site everybody's got great insight and yes I rewired the entire boat (so I don't have issues later). The last project replace alternator (increase demand from stereo amps) clarion ax480 pushing 4 polk MMC650 and a 10" powered sub. Just wanted to make sure if I should go with the one wire off the alternator Or do what 79 Nautique did with his alternator.

I have not tried staying with the factory 35amp but I think it might become an issue. I beleive in preventing problems not repairing them in the middle of the lake.

Thanks to everyone for advice

   Watch out for wattage on steroe amps. There are several means of measurement (RMS, Peak, Peak to peak) and most will give you the absolute watts output at a particular frequency. I worked on those amps in school and its funny to see 100 watt amp with 7 watt output amplifiers. Some of the real $$$ amps are in RMS and are accurate and will draw tons of current. Like 79N said, It may have a 25 A fuse for a 400 watt amp, which would mean the amp is not really 400 watts!! Just for your info, in loudness, a typical police car siren is 100 watts.

Jeff; There sure is lots of interesting stuff on here, just not sure how much of it I understand. I just thought all I hadta do for more volume is crank up the knob on the left.

john

Tony I would go with the 50 amp model from skidim with the internal regulator. You could use a 80 or 100 amp 10 or 12SI alt if you want. The one from skidim is going to be the easist(sp) to wire that is provided that when you re-wired everthing you basicly kept the stock configuration. The main thing is getting rid of the external regulator.

   I have the same amplifier that Tony is talking about above (clarion apx480m), it puts out 4x80 watts rms at 14.4 volts, a fair amount of power. The unit has (2) 25 amp fuses, and draws according to the manufacturer 46 amps at peak power. Between the head unit, the powered subwoofer and that amplifier your going to be 65 amps easy on the stereo alone, forget about it when you add tower speakers and another amplifier down the road (alright that might not apply to you but it is how I am thinking) you should go significantly bigger than a 50 amp alternator IMHO.
      I also doubt the polk mmc650's will handle the amplifier your using, they are only rated for 60 watts rms continuous. They are quality speakers and I am sure if you don't crank on them they will last a while but they wont take continued abuse at that power. Maybe return them and buy some JBL ms920's from Overtons... they are 6x9's so they might not fit, but they are 100w rms and overtons currently has them on sale very cheap. I like the idea of changing the wiring to a fuse box like setup, I think I will borrow that on my project, I will probably power the amplifier seperately though and rely on the two built in fuses. I haven't sourced my alternator yet, so if you find something good let me know..
-Joe.

Joe does the amp have two power feeds? I would doubt that it does and most likely all that the amp will draw at most is 23 amps. theres no way that it can draw more. I have a sony explode 300w continous 800w peak amp which has two 25 amp fuses as well and I have a ampmeter as well and have never seen it draw more than 20 amps with the engine running or off. And you won't find anyone that drives a stereo harder than I do. I have mine adjusted so that I can run it a max volume without any noticable distrotion and It does stay at this level for hours on end and I have never had a problem. Personally I think the 100 amp is over kill and a 50-80 amp model would work fine, but to each there own. Tony I'll have to look at your listing and get back with you. It sounds like you have done this under the dash and it would have nothing to do with the engine wiring harness but I'll take a look and get back to you.

Where are not talking about output voltage or watts, we are talking about consumption by the amp or what current the amp will draw under loaded conditions. So how the amp is rated for output is not relavent.

Bottom line if you are only adding one amp the stock 51A alternator is going to work fine, you could even add another smaller amp and not have a problem, now if you are going to use three or more then that's another story. You should be more worried about what size battery you have in the boat than the alternaotr's output because a group 24 battery isn't going to get the job done for very long and you'll be sitting with the boat idling to keep the battery charged enough to crank it over.

Geez I took to long to write that one, two responses while I was typing...

Tony,
   There is a standard for amplifier output, the CEA 2006 Mobile Amplifier Power Rating Standard. It is voluntary and not perfect (i dont think they should rate at 14.4 volts personally) but it is a good step, I decided only to buy certified amps and decks since the standard came out. Might as well patronize those that try to compete on an equal footing..
79 Nautique,
    Lets not start comparing the size of our subwoofers ;-)... I haven't even bought any yet... Haven't found anything marine grade that is powered and worth the effort yet, am in the hunt now. Would like to stick with some powered ones simaler to the basslink IIs that I have in my truck so I can avoid a second amplifier, they are 250watts rms each. Might eventually just buy the automotive ones and get my friends in the electrical lab here to conformal coat all the boards. My battery is a marine cranking battery.. its just pitiful in size since that is all that would fit after the last owners hack job on the battery box. I have a few 1000cca (1300 mca) marine cranking batterys in the rotation for my outboards, the Decoy will get the same this year. The rectifier on a mid seventies outboard makes a 35 amp alternator look positively awesome, luckly the outboards can be pull started with a little ambition.
    As for charging quicker, I think it depends on how much power you are pulling when you are charging and how fast you are driving. At 2000 rpm where I am wakeboarding I am only going to get about half the rated output of most alternators, that would give me maybe 30 amps while I am running the stereo, perfect pass, depth finder, and the ignition which could be drawing that much or more if I am cranking it I could see this being a net loss or at the least not enough to help me recharge the battery after running the stereo all day.. and of course I still havent ruled out those powered tower speakers somewhere down the road yet..
-Joe.

Slow down you mean to tell me if I only want to use 1 amp and a small powered sub no reason for me to upgrade alternator. Sweet I do have 2 batteries on board using a contionus duty solenoid to help keep both batteries charged I like this set-up better than the isolator been there done it.

79 rewired under dash installed inline protection 50 amp before going to fuse block.

still have the 50amp circuit on rear of engine

Tonydjd, if you are only going to use that clarion amp then you don't need a bigger alternator, but you do have to worry about the type and size of battery you have. If you are going to add more amps later then ya maybe a bigger alt might help, but when your sitting there with the engine off and the jams kick'n it doesn't matter if you have a 200A or 50A alternator they are going to charge up the battery at about the same rate when you start it up. Now if you have several amps and are crank'n it then you can have an electrical issue and loose power to the ignition and engine if the alt is capable of producing the need amperage.

Sorry if this is starting to bore people, I can't go out boating or even working on the boat for a couple months so I have nothing better to do...

The way I see it if the max output of the alternator is reached (and it is dependent on alternator rpm, which is determined by pulley size and engine rpm) by a combination of the various loads and the current that will flow into a battery at 14.4 volts (dependent on the internal resistance of the battery at the time) then the voltage will begin to fall below 14.4 and the regulator will not be able to keep it up. Once the voltage begins to fall the battery will charge at a slower rate, eventually with greater loads the voltage will drop below battery voltage and the battery will actually drain even though the alternator is putting out its max current at that alternator rpm.
     I used to be able to see this first hand in my 1985 RX-7 which had a very high current ignition system a lousy little alternator, and would idle around 500rpm. In the winter at night with the lights on and heat blowing I would have to rev the engine to keep it going, and that was with a new alternator and the biggest battery that would fit. The claim from the mazda garage was that the alternator pulley needed to be smaller due to the 7k redline, so it would never charge at such a low idle and that was only a problem if the battery was too cold to provide enough cushion at idle.
     Thanks for looking into the subwoofers, I think the 80w rms each to the 4 jbl 6x9s will be strong and sound good, but I would like to relieve them of the burden of also carrying the low frequency, the amp has a built in crossover and I would like to set it at about 400hz and find some subs that would still get some lows out to off the boat.. I don't think it will be enough for a wakeboarder to hear over the straight pipes, but maybe a wake surfer?
-Joe.