Additional New Alternator Source & Maine Sail's Analysis of Alt. Sources

[karista]

Last weekend while 20 miles out on the gulf, the RPM Gauge stopped working and the link showed no AMP input reading. Checked and re tightened all the wiring to the alternator and panel, still no readings.
The following day I emailed Westerbeke to get the OEM Model number for my original alternator. They replied by providing me their part number #42847 (Not model number) and their price for this alternator of $550.50. I questioned their high price and was told the following: "The reason the Alternator part #42847 is as expensive as it is, is in part due to the fact the Westerbeke disassembles the alternators and makes some mechanical changes to make it work properly and reassembles it. It's a time consuming and expensive process".
I then removed the alternator and found it to be a Prestolite 51AMP Model 8EM2017KA which has now been superseded by Prestolite Model 8MR2091KSS,

I then bought this Prestolite Leece Neville alternator, brand new for $179 from spidermarine.com  Its installed and works perfectly.


The vendor rep also told me that they have a 72 AMP Model 8MR2058PA ($179) and a 90 AMP Model 8MR2069TA, ($199) which many buyer prefer for the higher output and direct fit. Yes, I know of the Blue Circle High Output Alternator, but wanted to keep my installation as simple as possible and not have potential heat problems..

[Stephen Butler]

Westerbeke is part of CaterpillarCo., which does have higher prices for its parts.  The rationale justifying this is the stocking levels and speed of customer support.  Do not wish to start a thread on this topic, but rather to explain the situation.  Yes, I was in the CAT world for decades and yes, I now shop for my parts elsewhere.   

[Ron Hill]

Bernd : At those costs, I'd get a Balmar Hi -output alternator (max 100amp) and a smart Max regulator.  You'll be money ahead and really be able to send Amps to your battery banks in short order.  A thought

[SeaFever]

I wonder how would the Balmar 100 Amp alternator (with regulator) compare with the 90 AMP Model 8MR2069TA, ($199) Alternator Karista has mentioned. For 10% less Amps (on paper) it seems to be a great price...Hopefully someone has experience with both to tell us.

[Bobg]

Ron, and Karista,  I too am having charging problems,  with my dvm, I can get anywhere from 16 to 19 volts by touching the bat terminal on the alternator and the engine ground, funny thing is that the volt meter shows those volt readings extremely briefly and goes to zero right away after reading  16 to 19 volts.  my batteries are down a bit so the Alternator should be working but I get zip.  I am going to take it off and bring it to a auto shop to test it. I have a external regulator, upon commissioning the boat last month, the gauge read 14 volts the first time out, I thought all was good, but hasn't since.  My tack is working, although last year it read zero briefly, but started working again, albeit no charging.

So if the alternator is out, where do I get one of those Balmar Hi output and smart max regulator, and is it a direct fit from the old 55 amp stock Motorola Alternator I have?  Ron, I see on your motor you have two of them, not sure I will go that route, don't use the boat enough.

Isn't it kind of wierd that the tach started working again, but not the charging system ?  Thanks guys  Bob

[jmnpe]

Hi guys,

Having just been through this whole subject on our boat, there are a few things you need to consider before you make your "easy" upgrade to a high output alternator, or basically any alternator different than the old Motorola/Prestolite 51 amp alternator that came standard on the M-25 series engines with the upgraded alternator mounting bracket.

Here is the short version of the story. Any other alternator that isn't identical the original Motorola/Prestolite body, size, and shape will not just "bolt on" without a series of engineering design changes in the installation. (1)The body diameter of the original Motorola/Prestolite unit is only 5 inches: any "small frame" Balmar, Ample Power, or Delco unit will generally not fit because the body minimum diameter is at least 5.5 inches and will have to lean another 45 degrees or so to port to clear the engine block. This means you will have to fabricate a new alternator tensioner arm to allow the alternator to swing out that much more. (2) An alternator with a standard Ford ( 1") or GM ( 2") foot will not fit the 1.75 inch spacing of the alternator foot mounting on the standard engine mount. While you can use a .75" rather than a stock 1" Ford to GM adapter spacer, the .75" spacer is not a standard auto alternator adapter size. (3) There is a .125 to .188 " offset between the alternator foot mount front face and the tension bracket front face of the original Motorola/Prestolite alternator. On any of the previously mentioned upgrade alternators that offset is normally non-existent ( i.e. "zero" ).
(4) The cooling fan diameter on the original Motorola/Prestolite unit is smaller than any of the new upgrade fans, and this will translate into clearance issues with the stock alternator tension bracket.

All of this can be dealt with, as many in the group can attest. However, just be aware you will not be able to just order that nice new alternator and it's external smart regulator and go out to the boat on Saturday afternoon and "bolt it on".

Do your homework and research the Projects data and forum search engine results to be sure that you realize what you are getting into. There are higher output versions of the original alternator frame size available, but you won't find them in a West Marine or Defender catalog.

On our first C34 ( Hard Times ), and 1991 Mk 1.5 with the M-35 engine, many of the problems associated with the M-25 alternator mounting were not present. With nothing different other than a slightly smaller alternator cooling fan and some washers to shim the alternator into proper position for acceptable pulley/belt alignment, the upgrade to a 100 amp Ample Power alternator with remote smart regulator was pretty simple.

Just a heads up....

John

[karista]

John
You are correct re installation issues, that was the reason why I purchased the standard 51 AMP Prestolite alternator. Installation was simple and straightforward. In doing my research I found that the 72 and 90 AMP Prestolite Models also have the same footprint and are direct fit. They come standard with internal regulators, but many on the 36 Forum report installing the 90 AMP unit with a external regulator. There is a very detailed installatin report for the 90 AMP unit on their site. Personally, if I were to install a high output unit I would purchase the Prestolite 90 AMP unit at less than 1/2 the cost of the Balmar, and only install the external regulator if I found that the standard internal regulator was insufficient.

[pjcomeau]

Which engine do you have? I have the M25XP. I have the original alternator on mine or at least I think so. I thought I checked and it matches what others has described as a 55amp from Motorola. Which engine has this 51amp from prestolite? I'm looking for a simple replacement. As I've indicated in other posts, our season is short and rarely do we go out more then 3-4 days.

But if what some of the previous responses are true, then there is not much value in going to a higher amperage since internal regulators are designed for recharging the starting battery. Yet most people in my club still only have internally regulated alternators have have upgraded to higher output alternators.

So, I know external regulators would be the ultimate answer, but is going to a higher output internally regulated alternator going to improve my recharging time of my house battery?

Thanks

[karista]

Pierre
I have the 25 MXP, its a 1990 Model. I removed the standard Alternator and copied down the Model Number and the AMP rating which was on its data plate. If others are quoting a 55 AMP Motorola then maybe Universal used different models, however I could only find the 51 AMP Prestolite model listed on Prestolites site , no 55 AMP is listed.. Have you checked your alternators data plate to truly see what you have?

[waterdog]

If you upgrade to a high output alternator, make sure you maintain a diagram and the wiring to reconnect your old alternator.   Run your engine with the alternator door open if your bank is deeply discharged.  They produce a lot of heat and they cook themselves.   I've fried mine twice and I'm currently running with the old reliable Motorola.   

If you pull into a major service destination like La Cruz, a stunning portion of cruising boats are sending their high output alternators out for rebuild, Balmars, Ample Power, whatever...    Everybody has one or more spare alternators and has a love hate relationship with their alternators.   

Nothing comes for free.  Their is a price to pay for the extra electrons. 

[Ron Hill]

Guys : What Bernd hasn't said is that he has wind gen, solar panels and a Honda.  He figures app he really needs is the OEM stock engine generator.

FYI : About half of the early Universal engines (C34 1986 - 1993) came with a Motorola and the other half came with a Pestolite alternator. 

[Hawk]

Interesting, as just yesterday I was motoring into the marina at 1100 rpms when the RPM needle dropped to 0 and the engine changed pitch then popped back to 1100. Did this three times. I went to neutral then back into gear and it seemed to stop. But the same thing happened 2 weeks ago. All other displays were fine and my alternator and display panel in the cockpit connections were tight.
Thoughts?

Tom

[karista]

Tom
My symptoms were exactly as yours, RPM needle was jumping on and off, engine noise pitch changed, then back OK. A week later, same symptom again, but then the RPM gauge stayed at 0 and my Link showed no charge to the batteries. Time for a new alternator!

[Ed Shankle]

Tom,
Are you sure about all other gauges not changing? Reason I ask is I've had the tach problem as well, and the volt meter dropped to 11.5 - 12 volts at the same time. I think some others ID'd the same. John Nixson provided some possible explanations and tests to run on a string of previous posts. If you search tach problems you'll probably find it. I still haven't found the source of my problem, so I can't advise further.

Ed

[Stu Jackson]

1.  But if what some of the previous responses are true, then there is not much value in going to a higher amperage since internal regulators are designed for recharging the starting battery. Yet most people in my club still only have internally regulated alternators have have upgraded to higher output alternators.

2.  So, I know external regulators would be the ultimate answer, but is going to a higher output internally regulated alternator going to improve my recharging time of my house battery?

1.  Oh yes there is.  A higher amperage alternator will output MORE amperage at any given cruising speed, REGARDLESS of what type of regulator you have.  More amperage, less time to charge.  Internal regulators are tapering, meaning they don't provide a three stage charge and, first, they take longer to charge (and at a constant voltage) and second, they do not provide what battery manufacturers have been saying for years is the best way to recharge batteries.  That's all.  Most alternators, regardless of regulator type, will provide a reasonable charge to your battery banks between the 50% and 85% discharged rates because of BATTERY ACCEPTANCE, which is high when they are more heavily discharged.  No alternator will, within any reasonable amount of engine running time, completely fill up your batteries, regardless of regulator type.  Don't mix the regulator type with the ability of an alternator to recharge BOTH of your battery banks.  Besides, your start (reserve) bank rarely needs a charge anyway.  Internal regulators were designed for cars, but will also provide output necessary to recharge your house bank.  Period, they've been doing that for years, but have obvious shortcomings, discussed at length here on this message board and in most boating electrical system books and articles.

2. Yes, see above.

Your choices are simple:

a.  Internally regulated OEM 50-something amp alternator --- longest time to charge

b.  Internally regulated higher output alternator  --- improved charging because of more amps, means less time to charge

c.  Externally regulated higher output alternator  --- best bang for the buck in getting the most out of your investment in both the higher output alternator and your expensive batteries, least time to recharge

This is because the BULK and absorption phases initiated by the external regulator inputs more amperage, and thus charge, than an internally regulated tapering charger - these phases are written up in detail in every modern charger manual and all external regulators - pick the MC612 regulator at, say www.balmar.net and just read how the three stage charge regimen works - by now this should be basic battery charging technique stuff - also, as I've suggested many times before, download and read the Ample Power Primer, Tech Tab at www.amplepower.com - everyone should read this one!

And, remember: a reasonable charge to your battery banks FROM YOUR ALTERNATOR is between the 50% and 85% discharged rates.  For a COMPLETE recharge you NEED to connect to shorepower eventually.  Or get SOLAR.

Here's a link to an alternator vendor.  It's to a larger amperage alternator, just to get you to their website.  Please do not just blindly order this particular alternator, it is only to get you to that website.  When ordering any alternator, make sure you  get the right mounting.

http://www.ase-supply.com/Leece_Neville_110_603_12V_90_amp_ALTERNATOR_p/mo-110-603.htm