I'm doing some work to my engine that's in my Hallett, and I going to order a new alternator. My question is what amp alternator should I be looking at? I have a 454 BBC, 1-wire alternator, with 2 batteries, 4 Kicker 8" speakers and 600 watt 4 channel Fosgate amp, with auxiliary cable that is ran to my iPod. With that being said, should I go with a 80amps or 100amps alternator or bigger?

Like crew chief said it really depends on your plans but a alternator will only produce as much as needed so technically you can never have to big of a alternator but you can definitely have a alternator that doesn't put out enough. So it really depends on how much you wanna spend vs what you really need.

But if you are not afraid of a little electrical work and research a early to mid 90's caprice alternator may be your best bet. Just google "caprice alternator swap" and dig through a few forums. The caprice alternators are roughly a 140 amp alternator and are considerably cheaper than going out and buying a labeled "high output" alternator.


Edit: after a quick look it seems 90-93 alternators are a 120 amps and run around 100 bucks and 94/95 are 140 amps for around 140amps

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Like crew chief said it really depends on your plans but a alternator will only produce as much as needed so technically you can never have to big of a alternator but you can definitely have a alternator that doesn't put out enough. So it really depends on how much you wanna spend vs what you really need.

But if you are not afraid of a little electrical work and research a early to mid 90's caprice alternator may be your best bet. Just google "caprice alternator swap" and dig through a few forums. The caprice alternators are roughly a 140 amp alternator and are considerably cheaper than going out and buying a labeled "high output" alternator.


Edit: after a quick look it seems 90-93 alternators are a 120 amps and run around 100 bucks and 94/95 are 140 amps for around 140amps

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SoCalPSD,
I will look into it. I think I'm going to a 80-100amp the price is $100-140 new. One question though, on those years caprice classics, is it a 1-wire, V-Belt alternator?

If you are going to run a big amp alternator on two batteries, I totally recommend a battery isolator AND a switch.

One wire alternators larger than a 63 amp are a little silly.... The 10SI was built to amperage's up to 63 amps and is plenty big enough for the average boat. To understand this, you have to know what they are doing with the internal regulator. It is "self excited" meaning the field for the alternator is being energized internally. All it really means is that the regulator is permanently powered from the charge lead.

The way they did it in the '70's is brilliant. They ran a resisted circuit (using a light bulb as a resistor) from the dash of the vehicle to energize the regulator, this voltage was much lower than the output of the alternator and would run the alternator harder to bump the volts.

I thought I said it already on here, but my post didn't stick for some reason. Optima batteries do not like to be "cooked" back to a full charge.


GT

I've been running 2 optima 31 series yellow top batteries and 1 std 31 series for the engine along with a 4 position battery selector switch and a 200amp alternator. My yellow top batteries do not list a charge rate limit as long as the temperature doesn't get too hot. That being said my 200amp alternator will take 3-4 hours of cruising to partially charge my Optimas. But that is after about 6-8 hours of jamming with a 5k watt 4 subwoofer 12 component speaker stereo system. On my 10 amp optima charger the batteries will take 5-7 days to fully charge after a lake trip even with my 200 amp alternator. I've had this setup for 5 years now.


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If you are going to run a big amp alternator on two batteries, I totally recommend a battery isolator AND a switch.

One wire alternators larger than a 63 amp are a little silly.... The 10SI was built to amperage's up to 63 amps and is plenty big enough for the average boat. To understand this, you have to know what they are doing with the internal regulator. It is "self excited" meaning the field for the alternator is being energized internally. All it really means is that the regulator is permanently powered from the charge lead.

The way they did it in the '70's is brilliant. They ran a resisted circuit (using a light bulb as a resistor) from the dash of the vehicle to energize the regulator, this voltage was much lower than the output of the alternator and would run the alternator harder to bump the volts.

I thought I said it already on here, but my post didn't stick for some reason. Optima batteries do not like to be "cooked" back to a full charge.


GT

GT Jets,

I have a battery isolator switch, which gives me the option of "both, 1, 2, or OFF". From your reply, I'm assuming Optima batteries won't do me any good, if I keep them charged to 100%

I've been running 2 optima 31 series yellow top batteries and 1 std 31 series for the engine along with a 4 position battery selector switch and a 200amp alternator. My yellow top batteries do not list a charge rate limit as long as the temperature doesn't get too hot. That being said my 200amp alternator will take 3-4 hours of cruising to partially charge my Optimas. But that is after about 6-8 hours of jamming with a 5k watt 4 subwoofer 12 component speaker stereo system. On my 10 amp optima charger the batteries will take 5-7 days to fully charge after a lake trip even with my 200 amp alternator. I've had this setup for 5 years now.


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This somewhat validates my point.

The reason it takes so long to bring then back up the because they don't take a lot of current at one time.

You can do the same thing with a 63 amp alternator. You are not getting 200 amps out of your current set up.

GT

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I am actually getting damn near  200amps out of the alternator at 4k rpms, I have 2/0 wire from the alternator to the switch as well as all grounds and leads going to the front batteries. I used a fluke amp clamp to verify, only thing that holds me back from charging more is the v-belt setup, if the belt isn't brand new it slips.

Dude, I am not saying you are wrong, but do you know how many watts that is?

The amount of heat that would generate is ridiculous. 2800 watts of power would be incredibly difficult to believe. My 175 AMP Mig welder uses less power.

I think the largest Yellow top is 75 AH, that would be recharged to full capacity (or stupid close to it) in about 15 minutes.

Don't know how else to say it.

Not trying to poke you in the nose either.

Been doing this a long time. I was an automotive auto electric tech in the off seasons for a Chrysler dealer. We had one of the 130 amp grapefruit alternators in a Chrysler LeBaron full field because of a shorted output in a computer, it literally blew the battery all over the shop....

GT

2800 watts is equal to a crankshaft loss of over 4hp. That's why you can't keep a belt on it.

I would rather put that 4hp to the pump.

I have to wonder where all that current is going. To ignition system is probably using about 6 amps.

GT

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This is on a cruiser boat that has a sbc in it, I/O. All I know is that this has worked flawlessly for years and never had an issue. I built the boat for what I wanted to do with it, 4hp loss-really? Who gives a shit about 4hp when you have more than 700lbs of stereo equipment In a 6500lb boat? I don't want piss on my boots so I'll step out, have a good day!

I may have said that poorly, I am saying anything more than 1.5 HP requires double belts.

The other part of it is I have no idea where the extra approximately 100 Amps are going. An Optima cannot take that much current. I never said they aren't rated for the current, they just wont take that much charge at one time.

GT

GT Jets,

Doing that isolator seems like too much work, more than I asked for. I checked my boat out yesterday, and the alternator that's on shows 37amps. My guess is to just stick with a low amp alternator. I don't think I'll go with a high amp any more. Do to the fact that it can cause problems down the road or river.

What brand alternator do you have?  If you'd already have a Delco Remy it would take vertu little to convert it to a 63 amp worth literally no ill effects.

The isolator really is not that much work imho.

You have to run the charge wire to the isolator the each battery gets its own charge lead from the isolator. Done.

The advantage is that when you stop to hang out, you can run off of one battery without killing both.

What I do is keep the battery switch on one or the other and run the stereo power and the automatic bilge pump of the "axillary" battery.

Works like a champ.

Let me know if you need any information on how to wire it up.

GT

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I've never heard of Motorola myself.

That is actually a decent alternator. Very clean power compared to a Delco.  (No electrical noise).

They were later replaced by Mando.

Is your engine covered?

GT

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