Alternator upgrade on Westerbeke 40A

JDLanglais · **Joined:** 27 Jun 2007 11:23 **Posts:** 40

Hello all !

I am in the process of upgrading my house battery bank to 400 Ah on Judi Lou, and now I'm considering replacing the stock 51A alternator on my Westerbeke 40 by a more appropriate one (at least 70 A).
I know that some of us did that at some point.

Anyone did that with this model of engine ?
What brand of alternator did you choose?
Did you had to make modifications to the engine (changing pulleys, brackets, etc) to fit the alternator?
Any other issues that you had to face doing this upgrade ?

I briefly contemplated adding a second dedicated alternator on the engine but after few searches for the hardware needed from Westerbeke distributors; I had to conclude that this is very very expensive (the additionnal brackets and pulley needed would cost at least a thousand dollars without the alternator !!).

Thank you for sharing your knowledge and have a happy (and hopefully not too long) winter !

Jean-Denis
Tartan 37 # 162

berwick · **Joined:** 21 Oct 2006 18:12 **Posts:** 325

I was thinking when I upgraded I would do this serpentine kit from TAD http://www.tadiesels.com/sepentine.html then there should be less strain on the bearings etc.

Richard
#136
Salvation

Tartan37403 · **Joined:** 24 Oct 2006 12:51 **Posts:** 48

My T37 has a Westerbeke 33; but, did basically the same upgrade years ago you are contemplating. You might take a look at Ample Power's website. I used their 100 amp altenator, battery moniter, etc. No engine modification was necessary; works on a single belt. You do have to pay more attention to belt tension; but, no problems. Their products performed flawlessly for me. This winter I have had the top end of my engine overhauled and since the altenator probably had about a 1000 hours on it, had it sent out for overhaul as well.

I have about the same size house bank. I glassed in 3/4" plywood mounting platforms under the quarter berth and in the lazaratte to install battery boxes for 8D batteries. The only critical dimension I found was available height under the quarterberth. This arrangement has worked out well. Even with the old Adler Barbour refrigeration, a couple of summer days on the hook does not get us down to 50% discharge.

berwick · **Joined:** 21 Oct 2006 18:12 **Posts:** 325

To those that have upgraded - on my W40 the output of the alternator goes to the engine panel ammeter and then back to the solenoid and on to the battery switch. If I upgrade I will need to increase the wire size, so my thought is to just skip going to the ammeter and feed the bigger wire directly back to the house battery. I have a link 2000 so I can check current so is not the ammeter at the control panel redundant?

Thanks, Richard

Velera · **Joined:** 29 Dec 2006 09:38 **Posts:** 656

I did the same upgrade with Ample Power (100 A alternator into 4 Golf Cart batteries with Smart Alternator regulator) on my W 50 and found all of it very satisfactory for the last 15 years.

I believe you are correct that, given your situation, there is no need to run the line back to your ammeter. In fact, I think you will blow it if you upgrade as I think it has a limit of 25 or 30 amps of thru put.

Tortuga's Lie · **Joined:** 27 Oct 2006 10:32 **Posts:** 827

I am getting ready to do this upgrade. I have the W40 and bought the Balmar 7 series/80 amp with an external regulator (Defender had them on sale in the fall). Anyway, on the original Motorolla alternator, there are a lot of common grounds on a terminal that feed the instruments and oil pressure switch/alarm. I am assuming that I would re-connect these to ground but as Berwick stated, the red power coming off of the alternator goes to the amp meter. This is wrapped in a bundle, so I guess I would abandon this wire/ meter and monitor the external regulator for output? The new positive output wire should then go to the solenoid? If I abandon the power feed to the old amp meter, am I in danger of deleting a power source to anything else in the instrument panel?

jvoelxen · **Joined:** 21 Oct 2006 15:36 **Posts:** 268

I just bought a 105 amp alternator, which I'll be installing shortly, but I can answer your questions. I have a W50, which powers the instrument panel from the fuel pressure switch, but I suspect the circuits are the same.

1. Ground wires on alternator: Yes, you need to reinstall them. If you don't you'll lose some of the meter functions. I found this out the hard way.
2. Abandon/remove the alternator output to the Ammeter: You should have a Red #8 going to the ammeter, and a white #8 that returns to a terminal on the starter solenoid, which then goes to the battery switch. Nothing on the panel gets power from this source so you can remove it without any problem. If you chose to abandon it in place make sure you properly electrically insulate it. It will be powered when you turn on the battery switch. I'm running a new 6 or 8 gauge wire from the alternator output to the battery side connector of my windlass circuit breaker, which is close by. I chose not to go to the starter solenoid because it's very difficult to access on my boat. My boat has a 60 amp ammeter so I won't be using the old circuit for my alternator output. Also, it's a relatively long run, and I'm not sure putting 105 amps through it is a good idea.
3. Voltage regulator Connection: I have a Balmer AR-5 regulator. If I recall, the installation instructions tell you to attach the voltage sensing wire to the alternator output. I chose to connect mine to the common terminal of my battery switch. I did this because I knew there was about a 1 ohm voltage drop, at high charging currents, between the alternator and the battery so I wanted the alternator voltage output to be controlled by the lower voltage at the battery. Not sure it had any effect, but made me feel better.

Tortuga's Lie · **Joined:** 27 Oct 2006 10:32 **Posts:** 827

Thanks Jim.
Pretty clear that I can abandon the current amp meter loop and since I have a good battery monitor already, I can read the amperage input there. Unlike your setup, I think I can go from the new alternator to the battery input terminal on the solenoid. I did get a good response from Balmar this morning and they were very helpful as well. I sent them the wiring schematics from the Westerbeke 40 parts catalog.
When paying several boat units for an alternator and regulator setup, you don't want to screw it up and fry your investment..........measure twice, cut once. Shocked

Maine Sail · **Joined:** 16 Oct 2011 13:33 **Posts:** 12

Tortuga's Lie wrote:

I am getting ready to do this upgrade. I have the W40 and bought the Balmar 7 series/80 amp with an external regulator (Defender had them on sale in the fall). Anyway, on the original Motorolla alternator, there are a lot of common grounds on a terminal that feed the instruments and oil pressure switch/alarm. I am assuming that I would re-connect these to ground but as Berwick stated, the red power coming off of the alternator goes to the amp meter. This is wrapped in a bundle, so I guess I would abandon this wire/ meter and monitor the external regulator for output? The new positive output wire should then go to the solenoid? If I abandon the power feed to the old amp meter, am I in danger of deleting a power source to anything else in the instrument panel?

PLEASE DO NOT USE THE FACTORY AMMETER!!!!! Rant

I know you were not intending that but wanted to at least make that point so it can be seen...

These circuits are flat out dangerous with the factory alt and burn your boat down dangerous with a high output alt. they are also the main culprit in early battery death due to horrible voltage drop and chronic undercharging.

Rx=

1- Replace the Ammeter with a simple DC volt meter. Usually the alt output was a red and orange or red & white wire to/from the ammeter. Keep one of them for the volt meter and clearly mark and abandon the other.

2- Run the alt output to:

Starter Post - The alt current then picks up the large gauge battery wire back to the banks. DO NOT pass the battery switch through the OFF position when the engine is running. This is not "ideal" for many reasons but the #1 reason is improper voltage sensing. With the alt run though the batt switch the best you can do is sense the "C" post of the battery switch but this can still result in poor voltage sensing..

Direct to House Bank - with proper overcurrent protection within 7" of the house bank. OCP should be a bare minimum of 20-25% larger than the alts max rated output with 50% larger being much better as it will minimize voltage drop across the fuse..

Also wise to install a "service disconnect switch" for the direct wired alt to discontinue 12V at the alt terminal when working on the engine.

With the alt run direct to the house bank you can also properly sense the house bank + terminal.

If you want to see current I would suggest installing a battery monitor like the Victron BMV-600 which has a proper 500A rated shunt....

Westerbeke stopped this foolish and dangerous wiring many moons ago yet there are plenty of these high resistance, voltage dropping systems out there. Truly scary stuff...

With the Balmar the best performance will be in running positive and negative wires direct to the house bank. Size these wires as large as possible because even a 3% voltage drop at 14.4V results in just 14.0V at the battery bank and can lead to horrible charging performance.

Proper wiring minimizes voltage drop and allows the regulator to performs its duties and not have to over compensate for inadequate wiring.

I do not suggest grounding the alt to the engine block even though the 7 series is a case ground alt (not ideal but works). If you want the best performance run a dedicated new negative wire, same size as the positive, to the house bank or the house bank neg busbar. If you had a clamp meter you would see that 90+% of the current will take this new wire over the engine block path. Ultimately an isolated ground alt would be the best but the 7 series was never built that way, that I can recall.

jvoelxen wrote:

3. Voltage regulator Connection: I have a Balmer AR-5 regulator. If I recall, the installation instructions tell you to attach the voltage sensing wire to the alternator output. I chose to connect mine to the common terminal of my battery switch. I did this because I knew there was about a 1 ohm voltage drop, at high charging currents, between the alternator and the battery so I wanted the alternator voltage output to be controlled by the lower voltage at the battery. Not sure it had any effect, but made me feel better.

If this is the closest you can get the and alt output can be "switched" this is the best you can do..

The better method, performance wise, is to run the alt to the house bank and sense voltage at the house bank + terminal.

Voltage sensing can ONLY sense directly at a bank if that is where the alt B+ is physically wired to. Voltage sensing at the bank is the only way you get the best performance short of massive wires..

I have seen many owners cook batteries by improper sense wiring. Follow me here:

Alt goes through battery switch

Installer puts v-sense on house bank / #1

Owner selects start/aux bank #2 and fires up motor

Regulator see's no change in voltage at the house bank and continues to full field the alt driving the voltage of the start bank to exceed 17V+!!!!

Start banks survives this for a few hours then says enough already............

Tortuga's Lie · **Joined:** 27 Oct 2006 10:32 **Posts:** 827

Thanks Mainsail,
It's nice to know that you look at our forum on occasion Cheers

Love your website and I have purchased butyl tape from you in the the past as well as your prop!

I do have one question though after starting the install of the alternator: The old external Motorolla regulator has four wires. Three go to the old alternator: ground, field, stator. The fourth wire is a red that goes to the oil pressure switch then on to the positive of the old amp meter and other instruments. Is this red wire feeding the regulator or coming from it feeding the O.P./amp meter? I am thinking it could supply a low amperage current for the back-lighting of the instrument panel? In other words, can I abandon this lead or do I need to connect it to something and if so, what now that the old regulator is no longer there? The Balmar ARS-5 does not have this lead although it does have a brown lead that wants a switched positive that I have not hooked up just yet. Could this be the same?

I have upgraded the wire gauges and bypassed the old amp meter altogether.

Cheers,
Tom

Tartan37.com

Alternator upgrade on Westerbeke 40A

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