Cat 3208 Alternator Improvement

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Capt. Jon

Capt. Jon

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Joined
Dec 25, 2013
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Waypoint
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Californian 48' CPMY
I have looked around trying to find a replacement for the standard 51 Amp small frame alternator on the 3208. Would like to install a larger frame unit but the current mount will not allow it. Anyone ever tackled fabrication of a different mount to install a larger framed unit?
 
I've made several mounts during my working years for alternators and pumps on engines. The most important thing is locating the alternator so the belt alignment is true, the rest is just cutting, drilling and welding. I would build the mounts so I could adjust alternator position with shims to get correct belt alignment, washers will usually work for this.
 
Post your question on boatdiesel. Dave (not me), the resident Cat guru may have some ideas and maybe there is a Cat part available to mount a larger alternator. Dave will know. There are a lot of 3208s in service and you aren't the first person who wanted more amps.

51 amps? Even an 18 hp Yanmar diesel has a bigger alternator than that.

Also you might want to call Balmar. They sell high output, externally regulated alternators. A small case one that replaces the 55 amp Hitachi on the Yanmar noted above can put out 100 amps with a single belt, more with two. So they might have an alternator that could drop in to replace your puny one.

David
 
Tough one. The butt end of that little Motorola is real close to exh manifold. A big one is not going to fit there.
 
Balmar used to make a small frame 100 amp that would fit. I say used to, as I'm pretty sure I got two of the last three they made and this was a few years back. I use a center fielder in addition to the regulators to be able to pump both 100 amp alternators into a single bank. That's how I got to my 200 amps. I then use a charge controller to keep the starting bank up.

Otherwise you will have to make custom brackets and the alternator is going to have to sit in a not so great location. I might consider a real custom bracket to allow you to flip the alternator so it's not in the way.

I suspect somebody must make a high duty small frame alternator, but it might take some research. Maybe a call to balmar or an alternator shop to find someone to build one. I mean, once they put in decent bearings and diodes, that's pretty much it.
 
Ski in NC said:
Tough one. The butt end of that little Motorola is real close to exh manifold. A big one is not going to fit there.
Click to expand...

Yep, real close! Like just a few mm's!

It's been my experience with small frame high output alternators that heat soaking gets to them. Hence the question about the mount. Just thought someone had already done this and could post an example of what they did to solve the mounting issue. Just did not want to re-invent the wheel so to speak.

It maybe my best option are two small frame high output to get the amps I want.
 
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Presumably you need the amps to recharge a big house bank fast, right?

If so two of the OEM type alternators won't cut it. And particularly if you are going to the trouble of designing a second mount, make it so that it can handle a high output alternator.

First your OEM alternator is internally regulated. These alternators put out a fixed voltage and will not charge a house bank very fast. With an 80 amp internally regulated OEM alternator on my boat, it quickly drops back to 20 amps whereas an externally regulated alternator would keep the current high for much longer, thereby reducing charging times.

Even if you could add an external regulator, it is still a wimpy OEM alternator that is not designed to put out its rated amperage long term. High output alternators have better fans, diodes and heavier windings to deal with long term high output.

What you really need is a Balmar or similar high output alternator. Leece Neville and maybe Delco make some that are designed for emergency equipment that work fine at high output. But they are unlikely to fit your current mount.

David
 
Where are you located? There's a place in Oakland Ca called Northstar that repairs and rewinds altrrnators. They can do miracles with the stuff you drag in there. Look around and see if yours can be rebuilt for higher output.
 
motion30 said:
I replaced my stock alt with a 90 amp unit, exact same size
Click to expand...

Yes, found brand new prestolite 91 amp for $176 shipped. I can't even get my 51 amp Motorola rebuilt around here for that price!
 
Lutarious said:
Where are you located? There's a place in Oakland Ca called Northstar that repairs and rewinds altrrnators. They can do miracles with the stuff you drag in there. Look around and see if yours can be rebuilt for higher output.
Click to expand...

Orange Beach, AL. A longs ways away from Oakland! :D
 
Alternator improvement.

I had both my stock 3208 alternators rebuilt to produce ove 100 amp each. Don't know what they did but they work great.
 
When comparing alts ,always request the HOT rating.

It may be 50% of the cold rating, so not great for a boat , but really fine to run a car amp for a Boom Box car.

Size matters when it comes to cooling .

Some of the higher powered units for trucks and buses will use the engines oil to cool the unit.

90-100A HOT is a lot to ask from a small frame unit.

135 A from a large frame truck unit is under $150 brand new

To go cheap the old big cars (caddy) used 75A units with external regulators , that can be had rebuilt from Auto Zone style shops for about $50 rebuilt.

The Delco external regulator hookup will accept an aftermarket marine regulator.
 
Ski in NC said:
Tough one. The butt end of that little Motorola is real close to exh manifold. A big one is not going to fit there.
Click to expand...

Good point! In fact, make sure you have the rubber booty on it to!!!
 
It is pricey but you can get a smart charger that connects to your Alternator, that puts out 210 amps or as needed to your House bats.....anyone had any experience with that?
 
Any voltage regulation system is limited to the basic output of the alt.

Most alts are limited by their ability to cool ., which is why the HOT output is frequently minor.
 
Hack said:
It is pricey but you can get a smart charger that connects to your Alternator, that puts out 210 amps or as needed to your House bats.....anyone had any experience with that?
Click to expand...

Any information on this?
 
Have a Sterling 60 amp 3 bank charger on the boat now. Did not know they make such a device!
 
Capt. Jon said:
Have a Sterling 60 amp 3 bank charger on the boat now. Did not know they make such a device!
Click to expand...

Nor did I until I googled it to see what he was talking about :)
 
If you use Balmar MC-614 external smart regulators plus their CenterFielder to combine the output of two of the 91A alts mentioned above as fitting without needing special bracketing, you will be able to drive the alts pretty hard, safely....as the regs/Centerfielder come with alternator (as well as battery) temperature sensing. Shouldn't be hard to get around 160A out of that combo for bulk charging, with all going to your House bank....certainly way better than you are achieving now. And if you end up changing battery technologies down the track, the Balmar regs are fully programmable for different batt types, so somewhat future-proofing you too. ( I also recommend Balmar's DuoCharge to bleed off a controlled charging current from the House bank to maintain the Start bank.)
 
When a lead acid battery goes into acceptance from bulk charge the amps fall off during a constant volt charge say at 14.5 volts.

Are all the high amp rate charge references here for the bulk rate only? My bank of 400AH is not in bulk from alternators or xantrex 2000 very long.

Once I get to 14.5V the charge really drags out either way.

I plan to add more batteries and amp hours. And ditch the electric oven and stove for nice new safe propane setup. Main goal is maximize silence at anchor. Min genset run time.
 
If you use a programmable external regulator like a Balmar, you can set both minimum and maximum bulk charging times from alternators. You may be able to do this with the Xantrex also...not sure how programmable it is, but see its Operator Manual. You can set bulk charging time parameters with Victron & MasterVolt chargers. I've never used Xantrex but have noted many -ve comments about them on this Forum.
 
Capt. Jon said:
Have a Sterling 60 amp 3 bank charger on the boat now. Did not know they make such a device!
Click to expand...
Do you like it. Any info appreciated,I`m considering one to replace my ancient charger. Does it separately assess and tailor the charge to each bank,and if one bank is full does it send the full 60A to the one needing charge?
 
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