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Want to upgrade 351w alternator
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Hysteria View Drop Down
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    Posted: February-09-2021 at 10:39am
Anyone have a suggestion for a marine alternator that will bolt up to my '76 Nautique with a 351 windsor? I'm not terribly familiar with these motors and am guessing some people on here have already been down this road before me. I'm not too concerned about the wiring configuration, just looking for a recommendation that bolts up without too many fitment issues and is decent quality.

Thanks!
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Points: 11269 		Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: February-09-2021 at 2:52pm
Is this a PCM 351?

You could go to DB Electrical and get a 1 wire Delco marine alternator or a 3 wire Delco Marine Alternator or for a Mando replacement like what came on the mid 80's PCM engines, look at AMN 0002 from DB electrical.

They'll all bolt up with very minor modification.

The AMN 0002 will need a jumper wire between the "s" terminal and the output terminal and then it can be wired like in the mid 80's diagram below.

They'll all do away with your external voltage regulator on your 76






The picture below shows where the jumper would go on the Mando style alternator.

It's the strap between the "s" and output terminal with the black sleeve over it, but a 10 gauge wire works just fine.
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Points: 70 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Hysteria Quote  Post ReplyReply Direct Link To This Post Posted: February-09-2021 at 3:51pm
Thank you for the information! Yes, it's a PCM 351 in the boat. I'll get on DB electrical tonight and see if I can find a Delco that will fit, I'm just not sure about which model will bolt up to my motor. This is my first boat so I'm not familiar with any differences I would need to look out for with it being outfitted by PCM vs the normal 351 automotive application. I'm assuming the reverse rotation won't matter since it's rectifying AC current anyway, but correct me if I'm wrong on that.
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Grand Poobah
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Points: 11269 		Post Options Post Options   Thanks (0) Thanks(0)   Quote KENO Quote  Post ReplyReply Direct Link To This Post Posted: February-09-2021 at 4:14pm
Link to a 1 wire marine Delco style below

link

Link to a 3 wire marine Delco style below


Reverse rotation doesn't matter electrically and the cooling fan flow is plenty in either direction

Remember, more amp capability like the 100 amp plus ones that they have for example, (that I didn't link), means heavier wiring, bigger main breaker if your 76 has a breaker Wink
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Points: 70 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Hysteria Quote  Post ReplyReply Direct Link To This Post Posted: February-09-2021 at 4:49pm
Thank you for the links, that takes the guesswork out of it on my end. I'll be rewiring the whole boat so everything will be sized appropriately for its load, but that's a great point to make
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Points: 1010 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Nautiquehunter Quote  Post ReplyReply Direct Link To This Post Posted: February-10-2021 at 6:56am
I just put a DB 1 wire on my 67 Mustang 351w  .
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How do you like it? I went ahead and ordered a 3 wire last night from the link KENO provided
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I have had the one wire for several years.  works great and less confusion for my sometimes confused mind!
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Originally posted by Hysteria Hysteria wrote:

How do you like it? I went ahead and ordered a 3 wire last night from the link KENO provided

Hysteria, here's a post from a thread a little while back talking about 1 wire and 3 wire alternators. Either one will work good for you Wink

Originally posted by KENO KENO wrote:

Originally posted by NMiles77 NMiles77 wrote:

Ken post both pictures of the wiring
of the one and three wire Delco alternators, I was looking at them on DB website. The one wire is very tempting and the price is right.

Here's a picture of hooking up a 1 wire Delco

If you can count you'll say "but there are 2 wires" Wink

They don't count the ground wire for some reason. You don't really need the ground wire because the case is grounded to the engine through the mounting bolts and a lot of people don't use it but it's pretty easy to put it on.

Hooking up a 3 wire Delco (with 4 wires counting the ground)



Same Black ground wire hookup and Orange output wire hookup

The Red wire is the sensing wire for the internal regulator and in your situation hooking it to the output terminal works well.

The black wire next to it that's hooked to the green wire is the 12 volt excitation for the alternator. The Green wire color is just because that's what I pulled out of the drawer Wink

The 1 wire alternator is "self exciting". When you start the engine and rev it to a little over 1000 rpm's, the alternator is now excited and starts charging.Once it's charging, it will keep charging till you turn the engine off. Then on the next start, you rev it to 1000 or so and it's charging again. You can come down to idle speed and it'll keep charging as long as you revved it enough to excite itself.

The 3 wire needs 12 volts from a keyed ignition source to make it's regulator start charging. No revving it up is necessary.

The 3 wire can sense system voltage anywhere in the electrical system depending on where you hook the wire to.

In your case with a boat that doesn't have any big electrical loads, sensing right at the output terminal works well.

And.......since any of these alternators are a lot more powerful than your original the easiest way to protect your boat wiring which won't really handle much more than the original alternator's 37 or 40 or so amps is to put a 40 amp fuse right at the alternator output.

You won't use all the amps the alternator can put out if you get a 100 amp alternator, you're basically limiting it to 40 amps.

Some people just slap on a 100 or more amp alternator with no fuse at the output and can under the right circumstances melt wiring, make all kinda' sparks under the engine box and that's never a good thing

Here's a picture of a fuse setup that would work. The wiring to the fuse should be at least as big as the 10 gauge alternator output wire.

If you want to use all 100 or so amps, then to be protected you'd need some larger wiring all the way from the alternator to the ammeter in the dash and back to the engine again and you'd need the same size ground wiring.

The simplest but still effective setup would be the 1 wire alternator with a 40 amp fuse on it's output and the rest of your boat wiring could handle that.

Like with most things in life, there's more than one way to do do it, so maybe you'll get some other opinions.
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Points: 70 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Hysteria Quote  Post ReplyReply Direct Link To This Post Posted: February-10-2021 at 3:27pm
Another highly informative post. I ordered the 3 wire to avoid the issues you outlined with exciting the field, and I also like the idea of having control over the voltage reference that the alternator uses.
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