Which alternator for a Yanmar / Barrus Shire 1950?

[ditchcrawler]

I often wonder what the great desire is to fit two alternators when the engine one is doing next to nothing most of the time.

[Tony Brooks]

5 minutes ago, ditchcrawler said:

I often wonder what the great desire is to fit two alternators when the engine one is doing next to nothing most of the time.

 

Fashion & marketing.

[Froggy]

1 hour ago, Tony Brooks said:

Not just by too many appliances, also by very discharged batteries.  Belt squeal is actually the belt slipping on a pulley and a sit does so it tends to heat up and the rubber soften, that increases it's "grip" so it stops slipping and thus squealing.

 

Because of the peculiarities of your particular marinsation I can not advise you to fit a larger alternator. You may or may not get away with a larger one, but it is an expensive way to find out it does not work (2 alternators).

 

Ok, thanks again for all your help. I'll post an update when we have it sorted. As things stand we don't even know the rating of the alternator we've removed so it might be a bit of a gamble. I can't find the exact model anywhere on the internet, I'm guessing it went out of production about 20 years ago. I think I'll phone Barrus tomorrow, they've been very helpful in the past on two occasions, i even got to talk to a guy who helped develop this particular engine model (1950).

Edited August 31, 2021 by Froggy

[Froggy]

1 hour ago, ditchcrawler said:

I often wonder what the great desire is to fit two alternators when the engine one is doing next to nothing most of the time.

 

Yes, the alternator below only seems to charge the starter battery. I had been under the impression that it was charging the Eberspacher but i started the engine before removing the faulty one and no charge seemed to be going to the Eberspacher circuit.

[Tracy D'arth]

Just now, Froggy said:

 

Yes, the alternator below only seems to charge the starter battery. I had been under the impression that it was charging the Eberspacher but i started the engine before removing the faulty one and no charge seemed to be going to the Eberspacher circuit.

? The Eberspacher is on its own battery?  

 

With that belt arrangement and your history of belt wear I would not put a bigger alternator on.  A single V belt will just about run a water pump and a 90A 12v alternator. I have seen folk trying to run 100A alternators and in the morning when the batteries have lost charge overnight, they frequently cause belt slip and squeal which destroys belts and wears out pulleys.

 

You are running a water pump and 2 alternators now, the problem is that the wrap of the belt on the pulleys is insufficient already.

[ditchcrawler]

You could try paralleling all your batteries when you first start the engine and see if the belt handle it, if so you could connect both banks with a VSR and get the output from both alternators. That should put less load on the alternator pullies as it will be shared but the same load on the crank pulley,

[Froggy]

31 minutes ago, Tracy D'arth said:

? The Eberspacher is on its own battery?

Yes. But i don't think it's on its own alternator. That's what I thought I'd been told when we bought the boat, it's probably faulty memory, the fact that when starting the engine after the alternator failed the voltage didn't change on our Eberspacher-specific volt guage suggests i was wrong.

 

If we can't determine the amp rating of the faulty alternator and can't have it repaired do you think a 50 amp alternator would suffice for charging leisure batteries (currently about 240 ah from memory but ideally we would upgrade in the future to higher capacity). The downside of a low rated alternator would surely be longer charging time and hence greater fuel consumption and engine wear.

 

24 minutes ago, ditchcrawler said:

You could try paralleling all your batteries when you first start the engine and see if the belt handle it, if so you could connect both banks with a VSR and get the output from both alternators. That should put less load on the alternator pullies as it will be shared but the same load on the crank pulley,

 

I think that would be too much hassle since the starter and Eberspacher batteries are on the opposite side of the engine bay to the main leisure bank.

Edited August 31, 2021 by Froggy
Factual correction.

[ditchcrawler]

1 minute ago, Froggy said:

 

No, that's what I thought I'd been told when we bought the boat, it's probably faulty memory, the fact that when starting the engine after the alternator failed the voltage didn't change on our Eberspacher-specific volt guage suggests i was wrong.

 

If we can't determine the amp rating of the faulty alternator and can't have it repaired do you think a 50 amp alternator would suffice for charging leisure batteries {currently about 120ah from memory but ideally we would upgrade in the future to higher capacity). The downside of a low rated alternator would surely be longer charging time and hence greater fuel consumption and engine wear.

 

As I said, if you common the 2 you get the output from both alternators going into the batteries. Hopefully you wont have much more than 100ah to put in each day. Whatever you use you are unlikely to get below 3½ or 4 hours

 

[Froggy]

3 minutes ago, ditchcrawler said:

As I said, if you common the 2 you get the output from both alternators going into the batteries. Hopefully you wont have much more than 100ah to put in each day. Whatever you use you are unlikely to get below 3½ or 4 hours

 

 Please note I've corrected my post above and also replied to yours. The Eberspacher actually has its own battery but i think is charged from the same alternator that does the main leisure bank, i e. the alternator that has failed.

[Tony Brooks]

9 minutes ago, Froggy said:

 

No, that's what I thought I'd been told when we bought the boat, it's probably faulty memory, the fact that when starting the engine after the alternator failed the voltage didn't change on our Eberspacher-specific volt guage suggests i was wrong.

 

If we can't determine the amp rating of the faulty alternator and can't have it repaired do you think a 50 amp alternator would suffice for charging leisure batteries (currently about 240 ah from memory but ideally we would upgrade in the future to higher capacity). The downside of a low rated alternator would surely be longer charging time and hence greater fuel consumption and engine wear.

 

 

I think that would be too much hassle since the starter and Eberspacher batteries are on the opposite side of the engine bay to the main leisure bank.

 

1. Given a sensible way of running the cables, it would take me less than a morning. Two thick cables, one thin cable, and mount a bidirectional VSR.

 

2. I think I told you that no one can answer your question about a 50 amp alternator being sufficient until you do your energy audit and tell us how you use the boat and do battery charging.  I was happy for years with a nominally 60 amp alternator charging both battery banks, but then we were not big electricity users and did not have a 150 amp draw from an inverter.

[Tony Brooks]

4 minutes ago, Froggy said:

 Please note I've corrected my post above and also replied to yours. The Eberspacher actually has its own battery but i think is charged from the same alternator that does the main leisure bank, i e. the alternator that has failed.

 

In that case, it is not best practice. It suggests to me that at some time in the boat's life either the battery capacity was too small or the charging regime was insufficient. For optimum battery life, it is best to put all the batteries that feed domestic appliances into one bank. The larger bank will appear to have a slightly larger capacity than the separate batteries individually.

[ditchcrawler]

7 minutes ago, Froggy said:

 Please note I've corrected my post above and also replied to yours. The Eberspacher actually has its own battery but i think is charged from the same alternator that does the main leisure bank, i e. the alternator that has failed.

So how many batteries are you actually trying to charge each day, I am guessing 4 including the starter

[Froggy]

9 minutes ago, ditchcrawler said:

So how many batteries are you actually trying to charge each day, I am guessing 4 including the starter

 

Yes, 4, with two alternators, afaik the lower alternator just charges the starter.

 

When new the boat was fitted with four Trojan domestics, but the engine has been replaced with a different model in the meantime so it's possible that the original engine used two belts.

Edited August 31, 2021 by Froggy

[Froggy]

26 minutes ago, Tony Brooks said:

I think I told you that no one can answer your question about a 50 amp alternator being sufficient until you do your energy audit and tell us how you use the boat and do battery charging. 

 

The reason I'm questioning this is that the guy who diagnosed the alternator as being defective reckoned that 50 amps wouldn't be sufficient to charge a domestic bank. It would surely at least add to fuel consumption and engine wear on account of having to run the engine longer?

[Froggy]

28 minutes ago, Tony Brooks said:

 

In that case, it is not best practice. It suggests to me that at some time in the boat's life either the battery capacity was too small or the charging regime was insufficient. For optimum battery life, it is best to put all the batteries that feed domestic appliances into one bank. The larger bank will appear to have a slightly larger capacity than the separate batteries individually.

 

It might be because the boat was originally fitted out as a six-berth hire boat. At the time it had four Trojan domestics and from memory (we still have the original manual) it still had a separate battery for the diesel heater, which was originally a Webasto.

[Tony Brooks]

19 minutes ago, Froggy said:

 

The reason I'm questioning this is that the guy who diagnosed the alternator as being defective reckoned that 50 amps wouldn't be sufficient to charge a domestic bank. It would surely at least add to fuel consumption and engine wear on account of having to run the engine longer?

 

Fine, ask him and go by his advice, but don't come back here if it all goes wrong. I assume he did the power audit for you and the questioned you about how you charge and do the calculations before he came out with that.

 

Edited to add:-  better still get him to supply you with an insurance backed guarantee that a larger alternator will in no way shorted the belt life.

 

The fuel consumption of any engine is directly proportional to the load. Smaller alternator = lower load and lower fuel consumption, but running longer. Large alternator = higher load and higher fuel consumption, but running for less time. They cancel themselves out pretty much APART from the fact that half an hour or so after starting to charge it's normally the batteries that are controlling the charge, not the alternator's maximum output.

 

An alternator that is larger but that your single belt can reliably drive would only make a marginal difference to charge run time because after maybe half an hour the charge will have dropped to below the smaller alternator's maximum output.

 

Edited August 31, 2021 by Tony Brooks

[Froggy]

2 hours ago, Tony Brooks said:

 

Fine, ask him and go by his advice, but don't come back here if it all goes wrong. I assume he did the power audit for you and the questioned you about how you charge and do the calculations before he came out with that.

 

Edited to add:-  better still get him to supply you with an insurance backed guarantee that a larger alternator will in no way shorted the belt life.

 

The fuel consumption of any engine is directly proportional to the load. Smaller alternator = lower load and lower fuel consumption, but running longer. Large alternator = higher load and higher fuel consumption, but running for less time. They cancel themselves out pretty much APART from the fact that half an hour or so after starting to charge it's normally the batteries that are controlling the charge, not the alternator's maximum output.

 

An alternator that is larger but that your single belt can reliably drive would only make a marginal difference to charge run time because after maybe half an hour the charge will have dropped to below the smaller alternator's maximum output.

 

 

The main predicament here is that we don't at this moment know the output of our dysfunctional alternator. If this can be ascertained we can try to source a similarly rated alternator, or have the existing one repaired. If we can't determine this the dilemma would be having to guess and ending up with an alternator with an inferior rating to the original. If you think a 50 amp alternator would efficiently drive a service battery bank i will bear that in mind.

Edited August 31, 2021 by Froggy

[Tony Brooks]

29 minutes ago, Froggy said:

 

The main predicament here is that we don't at this moment know the output of our dysfunctional alternator. If this can be ascertained we can try to source a similarly rated alternator, or have the existing one repaired. If we can't determine this the dilemma would be having to guess and ending up with an alternator with an inferior  rating to the original. If you think a 50 amp alternator would efficiently drive a service battery bank i will bear that in mind.

 

Look, both Tracy  and me have told you that your setup is far from ideal and the belt squeal under load suggest it was already operating right at the margin of what is possible so it is not a good idea to put even more load on the belt.

 

Yes, a 50 amp alternator can and will service not only the domestic bank but also the start battery on many boats, but this may not be true of yours because you won't or can't tell us the results of your power audit. That will give an idea of how much electricity you take out of the batteries over 24 hours, and that in turn gives an idea of how much you will need to put back in. The back in figure will be maybe 20 to 30% more than you take out.

 

Having got that figure we need to know how you charge it and for how long each day, from that we can infer how long it will take any given alternator to fully recharge the batteries.

 

Without that data, how do you expect us to give you the answer you want?

 

As an extremely rough guide, a 50 amp alternator will supply about 100 Ah over 3 to four hours running. Running for longer produces ever fewer and fewer Ah per hours run.

 

I would expect any decent alternator specialist to recognise your alternator and have a very good idea of its output. I have no expectations that an Ebay vendor will have a clue.

 

 

Lets try this. @Sir Nibble please, can you have a look at the images on page one and give an opinion on the alternators' likely outputs. Thanks in advance.

 

 

[Froggy]

Tony, i am asking a lot of questions because i am a novice with electrics, but very inquisitive (and need to make a decision quickly since we are currently without power and have had to defer a fairly lengthy week's cruise until this is sorted). I appreciate all the advice you have given. No, we haven't done a power audit but our existing charging regime has kept us in good stead in the four years or so we've had the boat. The batteries still seem to hold their charge well about three years in and the belt has only been changed twice in over four years. The engine is probably only run on average for about 10 hours a week, apart from occasional longer cruises. We are normally very frugal with power consumption: the tv, fridge and vacuum are used very sparingly (the fridge is only used in very hot weather, mainly to cool drinks) and the microwave almost never; most of our lighting has been converted to led.

 

I'm going to phone Barrus tomorrow to see if they can shed any light on the alternators that might have originally been fitted / recommended for this engine. Then I'll await the refurbisher's report and take it from there. I'll report back on how this pans out, and obviously the advice you and others have given will help guide my decisions.

 

Edited August 31, 2021 by Froggy

[ditchcrawler]

10 hours ago, Froggy said:

Tony, i am asking a lot of questions because i am a novice with electrics, but very inquisitive (and need to make a decision quickly since we are currently without power and have had to defer a fairly lengthy week's cruise until this is sorted). 

 

You can get power by putting a jump lead between your domestic bank and your starter bank if you havent already removed the domestic alternator, just take the lead off when the engine isn't running

[Tony Brooks]

1 hour ago, ditchcrawler said:

You can get power by putting a jump lead between your domestic bank and your starter bank if you havent already removed the domestic alternator, just take the lead off when the engine isn't running

 

Not on a twin alternator on one belt setup you can't. That is what the OP has.

[Froggy]

1 hour ago, ditchcrawler said:

You can get power by putting a jump lead between your domestic bank and your starter bank if you havent already removed the domestic alternator, just take the lead off when the engine isn't running

 

Thanks for the suggestion but domestic alternator is now in for repair.

[Froggy]

Latest update on this is that a diode was blown. Alternator is getting an extensive refurbishment in addition to the diode.

 

Is it possible that fitting a belt that isn't an exact replacement could cause issues? The replacement belt was already on the boat but i did note the teeth were a little chunkier but just assumed it was due to wear on the older belt and/or different manufacturing tolerances. Both belts were as good as identical in terms of width and circumference. Taking a closer look at these close-ups now though there does seem to be a real difference in the profile of the teeth. The older belt is at the bottom in both photos.

[Tony Brooks]

Let's get the teeth out off the way first. They are only there to allow the belt to bend around a tighter radius and thus aid gripping on the smaller pulleys we tend to use, so that is very unlikely to be here or there.

 

What is vital, especially in your situation, is ensuring the new belts match the pulleys because with that belt size there are at least tow different cross-sectional profiles and if you get the wrong one it will not  grip across the full side faces of the belt, will wear faster and squeal more. The bottom belt has had it. If you don't know the belt profile/part number I think  I would buy a couple from Barrus but even then I had a case where they supplied the wrong profile.

 

 

[Tracy D'arth]

3 minutes ago, Froggy said:

Latest update on this is that a diode was blown. Alternator is getting an extensive refurbishment in addition to the diode.

 

Is it possible that fitting a belt that isn't an exact replacement could cause issues? The replacement belt was already on the boat but i did note the teeth were a little chunkier but just assumed it was due to wear on the older belt and/or different manufacturing tolerances. Both belts were as good as identical in terms of width and circumference. Taking a closer look at these close-ups now though there does seem to be a real difference in the profile of the teeth. The older belt is at the bottom in both photos.

I think that it is just a manufacturing difference providing the width  of the back of the belt is the same,

I would use a Gates belt, they are generally considered to be the best available.

 

The failed belt looks to me to have failed due to overheating due to slippage ( squealing )  rather than normal wear.