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Old 19-05-2015, 17:43   #1
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Alternator Selection for 30 HP

Hey all,

Going over a variety of systems on the boat and I'm stuck on alternators. I've read a bit, but thought I'd ask for opinions to see if anyone has ideas I haven't had yet...

I have two Volvo Penta MD2030's, that have a knockoff of the OEM alt on them. They're rated at 60 AMPS, but are cheapos and disposable ($140 ish). I would like to replace both and keep the current ones as spares.

Criteria (in order of importance):
- I want the replacements to be more durable, possibly even "marinized", and not eat belts
- I don't want to break the bank (Balmar's seem ridiculously expensive)
- I'd like to get a little more out of the alts than 60 AMPS, maybe 80-100
- I don't want to have to add different pulleys, belts, etc. Drop-in replacements ideal
- I'd prefer to have an internally regulated alt, just to simplify things and keep costs down. (I'll admit to being ignorant on this)

Other stuff that might help:
- 880 AH FLA house bank
- 680 W Solar on rear arch, run to MPPT controller, usually enough for my needs

And... Go.
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Old 19-05-2015, 18:26   #2
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Re: Alternator Selection for 30 HP

Quote:
Originally Posted by TheNomadTrip View Post
Hey all,



Going over a variety of systems on the boat and I'm stuck on alternators. I've read a bit, but thought I'd ask for opinions to see if anyone has ideas I haven't had yet...



I have two Volvo Penta MD2030's, that have a knockoff of the OEM alt on them. They're rated at 60 AMPS, but are cheapos and disposable ($140 ish). I would like to replace both and keep the current ones as spares.



Criteria (in order of importance):

- I want the replacements to be more durable, possibly even "marinized", and not eat belts

- I don't want to break the bank (Balmar's seem ridiculously expensive)

- I'd like to get a little more out of the alts than 60 AMPS, maybe 80-100

- I don't want to have to add different pulleys, belts, etc. Drop-in replacements ideal

- I'd prefer to have an internally regulated alt, just to simplify things and keep costs down. (I'll admit to being ignorant on this)



Other stuff that might help:

- 880 AH FLA house bank

- 680 W Solar on rear arch, run to MPPT controller, usually enough for my needs



And... Go.

Does ur rpm display come from the alternator?


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Old 19-05-2015, 18:43   #3
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Re: Alternator Selection for 30 HP

Depending on belt size you're going to be limited to around 70 amps to avoid eating skinny v belts. Also to make anywhere near the alternators rated power for any decent amount of time you'll need external regulators.


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Old 19-05-2015, 18:53   #4
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Re: Alternator Selection for 30 HP

I have a 100 amp Balmar with an external regulator. I leave it permanently jumpered to "small engine" position. Otherwise it eats small v belts in a few hours.
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Old 19-05-2015, 19:41   #5
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Re: Alternator Selection for 30 HP

Quote:
Originally Posted by Cap Erict3 View Post
Does ur rpm display come from the alternator?
Yep, but I'm not too worried about that. I can adjust those settings, if needed.

After some more reading, and the responses here - it appears I have three options:

- keep doing what I'm doing (cheap, but relatively crappy)
- pick up higher-end 70 AMP alts (halfway fix)
- do a total overhaul ($$$) on this consisting of a serpentine kit, external regulator (can I use one for both alts?), and a hi-amp alt (100 AMPs). for BOTH ENGINES.... that last part is a killer...

Or, maybe do a serpentine kit and hi-amp alt for both engines, skipping the reg? In this case I'll still be pumping in WAY more amps than before...


Jeez, this is a pricey subject.


Anything I'm missing?
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Old 19-05-2015, 20:04   #6
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Re: Alternator Selection for 30 HP

Quote:
usually enough for my needs
So why do you want to change?

Anyway maybe Leece Neville have something for you. It isn't necessary to have an external regulator, especially with the newer internally regulated alternators. What is necessary/desired is that the alternator be able to put out its rated power when it heats up without burning up. Of course ventilation helps with that as well. Having said this I personally would use an external regulator for many reasons, one of them being the belt saver settings another being able to derate the alternator output.
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Old 19-05-2015, 20:42   #7
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Re: Alternator Selection for 30 HP

Ribbed belts (they don't have to be serpentine unless you're planning to add self-tensioners) are great but while you're looking, look at the specs for the alternators.

Look for a spec for continuous duty output, not intermittent.

Look at the output/vs/rpm charts, and see how fast they should turn to actually put out that power. By adjusting pulley size, and picking an alternator with the right range, you can pick one with better output at idle speeds, FULL output at cruising speed, and not self-destructing at emergency speeds, i.e. fighting into a storm.


Figure out all that, then which alternators can be fitted into your mounts and spaces, and you'll probably be ready to go back to kerosene. Or, you'll have the right alternator.
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Old 19-05-2015, 21:33   #8
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Re: Alternator Selection for 30 HP

Quote:
Originally Posted by TheNomadTrip View Post
Yep, but I'm not too worried about that. I can adjust those settings, if needed.



After some more reading, and the responses here - it appears I have three options:



- keep doing what I'm doing (cheap, but relatively crappy)

- pick up higher-end 70 AMP alts (halfway fix)

- do a total overhaul ($$$) on this consisting of a serpentine kit, external regulator (can I use one for both alts?), and a hi-amp alt (100 AMPs). for BOTH ENGINES.... that last part is a killer...



Or, maybe do a serpentine kit and hi-amp alt for both engines, skipping the reg? In this case I'll still be pumping in WAY more amps than before...





Jeez, this is a pricey subject.





Anything I'm missing?



While there are plenty of things to spend outlandish amounts of cash on, good automotive alternators are tough and cheap. The tach output is easy to add if needed.




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Old 19-05-2015, 22:36   #9
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Re: Alternator Selection for 30 HP

Quote:
Originally Posted by DeepFrz
So why do you want to change?
Mostly because I can tell the alts on the engines now aren't high quality. I'm planning a trip across the S Pacific, which I hope to take years. And I'm sick, to death, of replacing low-quality crap.

In fact, in an effort to truly minimize the time I spend doing boat maintenance (maybe a pipe-dream, but a worthy goal) - it almost makes adding the serpentine system worth it - no more replacing belts, shredded belts leading to overheating engines in rough seas, etc.

Quote:
Originally Posted by hellosailor View Post

Figure out all that ...and you'll probably be ready to go back to kerosene.
This.

I'm tempted to go with the serpentine kits and a high-output alternator, with no regulator. The truth is, though, I have better ways to spend that money. Or I think I do...

I'm leaning toward the Leece-Neville 72 AMP, marinized alt for both engines, and using one of Mark Grassers' (V) pulleys on them. Don't care for the external regulation, I have enough electrical doo-dads onboard already. Prefer, instead, to undersize the amp a little and not worry about shredding belts.

For the alt, something like this:

Prestolite - Leece Neville

Any more thoughts? I'm a ways from pulling the trigger...
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Old 19-05-2015, 22:57   #10
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Re: Alternator Selection for 30 HP

There is also a 90 amp one as shown on Maine Sails how to site. Just make sure the mounts are correct for your engine.
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Old 19-05-2015, 23:44   #11
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Re: Alternator Selection for 30 HP

Quote:
Originally Posted by DeepFrz View Post
There is also a 90 amp one as shown on Maine Sails how to site. Just make sure the mounts are correct for your engine.
I'd prefer the 90 AMPS... But I think at that level I have to buy a regulator, right?

If that's the case, it's a whole new bag of worms - as I have to do that for both engines...
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Old 20-05-2015, 09:02   #12
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Re: Alternator Selection for 30 HP

Go with a high output alternator and 2 step regulator. I have used Amptec regs for years with Xantrex reg. No belt devouring from my 56 hp Yanmar. I charge 440 ah house bank plus start battery. Very reliable. I also have a rebuilt Amptec 105 amp reg available. Used it as spare on a crossing. Asking $200 with Xantrex reg.
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Old 20-05-2015, 09:07   #13
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Re: Alternator Selection for 30 HP

Good question, but you should do some more homework and then make your decision.

This discusses the advantages & disadvantages of regulators:

Musings Regarding External Regulation - SailboatOwners.com

You CAN run a hi amp alternator without one, but then it becomes a belt issue.

DeepFrz uses one technique, Small Engine Mode. I use it too, but have added a switch to it, so I can use full output when I choose.

Alternator heat, Regulator Controls, Small Engine Mode

Alternator heat, Regulator Controls, Small Engine Mode

Small Engine Mode - discussion with link to the picture of the toggle switch: Alternator heat, Regulator Controls, Small Engine Mode

Small Engine Mode - the picture of the toggle switch Alternator Output Management with External Regulators [Small Engine Mode]

I have a 100A alternator with a Balmar MC-612 regulator.

Good luck.

Your boat, your choice.
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Old 20-05-2015, 09:41   #14
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Re: Alternator Selection for 30 HP

While internally regulated are easier to install, wire up etc the downside is that they read "system" voltage at the alternator output, not at the batteries and thus, do not take wiring/connector condition etc into account. I have used internally regulated on my hot rods as the easy path but will only use externally regulated on anything that counts...like our boat...or my wife's car due to ongoing threat "if it ever leaves me stranded....".
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Old 20-05-2015, 09:58   #15
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Re: Alternator Selection for 30 HP

Quote:
Originally Posted by Wulf View Post
While internally regulated are easier to install, wire up etc the downside is that they read "system" voltage at the alternator output, not at the batteries and thus, do not take wiring/connector condition etc into account. I have used internally regulated on my hot rods as the easy path but will only use externally regulated on anything that counts...like our boat...or my wife's car due to ongoing threat "if it ever leaves me stranded....".
Many internally regulated alternators also contain connections for an external sense wire and a stator output, which can be used instead of the internal connections.

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