Alternator Upgrade

[bayates]

I am sure it has been asked numerous times but want clarification before I purchase the alternator.  I want the 90A internal regulator direct replacement.  We have solar for majority of our power replacement.  I want the direct replacement for the stock 54A unit.  It appears to be the Leece-Neville 90amp 8MR2069TA which I can find.  Is this the correct upgrade unit for plug replacement. We have a 2000 MKII with an M35B engine.  I appreciate the help. 

Brian

[mainesail]

I am sure it has been asked numerous times but want clarification before I purchase the alternator.  I want the 90A internal regulator direct replacement.  We have solar for majority of our power replacement.  I want the direct replacement for the stock 54A unit.  It appears to be the Leece-Neville 90amp 8MR2069TA which I can find.  Is this the correct upgrade unit for plug replacement. We have a 2000 MKII with an M35B engine.  I appreciate the help. 

Brian

Brian,

There is also the CMI-72-IR https://shop.marinehowto.com/products/cmi-72-ir-universal-diesel-marine-alternator which is a custom built drop-in replacement for the 51A 8MR2049K only in 72A version that deals better with the stock 3/8" belt. The CMI-72-IR can also be converted to external regulation in the future. The regulator can be pre-set during assembly/testing to what ever voltage you desire and the voltage adjustment is sealed inside the regulator not on the outside where the elements get to it and cause it to have regulating issues. The 8MR2069TA also does not come with a pulley, or the fit-kit, to turn it into a 2" foot mount.

[Ron Hill]

Brian : Mainsail is correct.  The two items that you need to look for in a new alternator is the matching pully and matching case attachment to the engine.   

You may have to go for an external voltage regulator, which you can program as you wish - which is easily done!!

A thought

[bayates]

All, thanks for the help and info.  I found what I needed with a 90A internally regulated alternator (100-600), adapter bushing (118-2 ) and pulley (24-4103) at Romaine Electric.  It will suit the needs on Hakuna Matata nicely. 

Brian

[KWKloeber]

Stock up on belts (use Top Cogs) with the measley 3/8" driving that 90 amp-er. 
An inappropriate mismatch there.

[Stu Jackson]

Brian,

You may be just fine.  Much depends on how you use your boat.  And how depleted the house bank, and how big it is, which determines startup amp draw, at cruising revs.  That alone will determine how hard the alternator has to work.

With an internal regulator, one could simply start moving the boat at lower revs until the initial high acceptance of the depleted bank is beginning to be replenished, at which time you can up revs without overloading a belt with that sized alternator.

I've been running a 100A alternator on a 3/8" belt for 20 years.  While I have an external regulator and use the Small Engine Mode,  what many of us have learned is that a 50% SOC house bank of 400 ah will accept 70A for about five minutes or so.

So a slow bell before getting up to cruising rpms works.

It's a delicate balance, and depends on how you use your boat.

[KWKloeber]

...one could simply start moving the boat at lower revs until the initial high acceptance of the depleted bank is beginning to be replenished...

Agree!  But then, what's the arguement for installing a big-a$$ gen only to throttle it back to what should be there to begin with?
(unless it's to buy it now anticipating a major upgrade in reg or serpentine down the road.)

[Stu Jackson]

...one could simply start moving the boat at lower revs until the initial high acceptance of the depleted bank is beginning to be replenished...

Agree!  But then, what's the arguement for installing a big-a$$ gen only to throttle it back to what should be there to begin with?
(unless it's to buy it now anticipating a major upgrade in reg or serpentine down the road.)

It's not an argument.

What it IS is consideration of the use of the available. 

The concept is to be able to continue to use a 3/8" belt for a majority of the time, without the belt slipping and squeaking under a heavy load on the alternator.
When does this occur?  When you have spent the night on the hook and your house bank is depleted.  So when your engine starts, the regulator on the alternator is requiring maximum alternator output, whether internally or externally regulated.

When you first start the engine, with low rpms, it is not an issue.  But as soon as you bring the rpms up to cruising speed while the house bank is STILL in its maximum acceptance period, ANY alternator will be producing as much power as it can, even an OEM nominal 55A alternator.

This is ONLY a pretty short period of time, because we all have had experience with how relatively quickly the amperage drops off as soon as we start charging, with the alternator or a shorepower charger.  It is the basic charging process, and battery acceptance.

I discussed this in quite some detail in my Small Engine Mode discussion, which can be found in the Electrical 101 Topic, in this post:  https://c34.org/bbs/index.php/topic,4454.msg26031.html#msg26031, and from page 2 of that same link:  https://c34.org/bbs/index.php/topic,4454.msg27149.html#msg27149

On a C34, Ken, there is VERY little room forward of the pulleys to easily mount a serpentine belt kit.  This is because of the companionway stairs, and is very different than the arrangement of a diesel inboard on your C30.  I am sure some have done so, but I do not recall having seen one reported on this website on a C34.  It would be interesting to see one.

But this issue is simpler:  How do I run my system while maintaining the 3/8" belt to minimize slipping and squealing?

The only time that happens is when initially charging a depleted bank.  After that it is not an issue.  Based on my linked experience, it is, perhaps, all of half an hour.

The concept of installing a high amperage alternator is also simple:  it works cooler than a smaller alternator given identical loads.

And the battery acceptance of a nominal 400 ah bank is in the range of 50A to 70A, which tapers off rapidly.

So, at startup, either run, once you're in gear, at a lower rpm for a short period of time, or use an external regulator either with Belt Manager or Small Engine Mode.

Once past the initial high load, you can open 'er up to full cruising rpm and STILL use your 3/8" belt.

However, with a smaller alternator, that would take longer, because the smaller alternator would still be maxed out, whereas the larger alternator would be working "less hard."

After that first half hour the acceptance will have dropped from the 50-70A range to 30-40A.  That would be a larger percentage of a stock 55A alternator, but half that for a 100A alternator  (55/100).  Yes, the load would be the same, but the alternator itself would be running cooler.

And, based on my mere 23 years of experience, that 3/8" belt CAN HANDLE a 30-40A load without slipping or squealing.  At cruising rpms.

An added advantage is, that in using Small Engine Mode, I can get twice the output at lower rpms if I use my engine to recharge my house bank at anchor.  Sure, solar would be better, but I don't have it.  I put the SEM into 100% and run at 1500-1800 rpm out of gear, and get twice as much output as I would with an internally regulated alternator.  And the belt doesn't slip or squeal.

That's why. 

[Ron Hill]

Brian : I don't know about your brand alternator, but most internal regulators in alternators only allow their hi rated amperage output for a Nano second!! Then they drop down to a fraction. 

That's why most of us with a Hi Ouput Alternator have gone to a programable external voltage regulator!!

A thought

[Stu Jackson]

Brian : I don't know about your brand alternator, but most internal regulators in alternators only allow their hi rated amperage output for a Nano second!! Then they drop down to a fraction.  >>>>>>>>>>>>>

As far as I know, Ron, only the Hitachi alternators do that because they have internal temperature sensors.  I discussed this with an important link from Maine Sail's excellent writeup about this in either the 101 Topic or the Electrical 101.

Hitachi Alternators 101  http://forums.catalina.sailboatowners.com/showthread.php?t=166123  This comes up so often on other boating forums...

The Motorola alternators that were OEM on Universal engines do not have this "feature" and will get really hot with no controls.  Only battery acceptance determines the load that is placed on an alternator [of course, at any given rpm].  That's why we recommend larger alternators which will run cooler with the same load and considering external regulation and temperature controls on the alternator, belt manager or SEM.

Your boat, your choice. 

[Ron Hill]

Guys : Another important feature of the new external voltage regulators, is that the regulator lets the engine run after start up for about 30 seconds before it "kicks in" the alternator loading.

A thought

[Mick Laver]

I've been using a standard regulator 90A alternator (Motorola 12V 90A Marine Alternator 110-603, pulley Mot 107-1, adapter bushing MOT 118-2) with the stock 3/8" belt for about 8 years with no issues. I have a 450AH flooded house bank (4 T-105s). If the batteries are depleted (100 or 200 AH down) the alternator will put out about 60A for about 15 minutes then settle down to 35-40. I'm sure an external programmable regulator could make the system more efficient, but I wanted something simple.

[KWKloeber]

Stu

Most excellent point about the benefit of running a high amp (90+) at 50%.  It's the same as I try to convince my 30-er brethren about "oversizing" their shore chargers but it often falls on deaf ears.  "15 amp is all I need."  sheesh.

I would think that using a good billet-machined pulley would help as well w/ a 3/8" belt.

I know that a few yrs back Rod had posted a pic that he thought, but not 100% certain, was a serpentine that he did on on a 34 (might have been a 36.)  I doubt we could do it on the 30 -- the space is way too tight (I think y'all have more room).  At a minimum it would need a reworked engine door -- extended even farther than is is now (frame extension about 1" was added when offering the M25 option in place of the Atomic 4) because my m25 actully extends OUTSIDE of the fiberglass engine enclosure! 

-ken