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Barrus Alternator Replacement

I have a Barrus Shire 1952LB (4Cyl, 2Ltr) engine of around 2002 build with two alternators. The water pump and both alternators are driven from the crankshaft by a single belt. The larger of the 2 alternators is mounted near the top of the engine and is stamped 'Mando Korea'. I understand it has an output of 80amps. I have a Sterling alternator regulator connected to this alternator for charging the cabin batteries (3 x 110ah)using the wire installed on the alternator by Barrus for this purpose. The original alternator failed after about 1200 hrs and I replaced it with a reconditioned unit from my local dealer. After a further 800 hours this unit has also failed. In comparison with the longevity of car alternators I find this quite apalling. My local dealer no longer has reconditioned units available and Barrus can only advise me to get it repaired. They also referred me to Nantwich Canal Centre centre who say that they regularly get these referrals but have no solution. Can you advise me where to get a replacement? I am prepared to have a reconditioned unit but would probably prefer to get a new and more reliable make of alternator if I can find something which will fit the existing brackets.
Also, I am told by various sources that the problem is most likely to be that the regulator in the alternator burns out. Is this because my engine compartment is too hot (cruiser style NB) or is the alternator actually unsuitable for a narrowboat application? What operating temp should an alternator be able to tolerate? Should I be considering some kind of forced ventilation? It may be that getting the existing alternator repaired is only a short term fix to keep me going for another 800 hours.
I hope WW or its readers can help as my present alternator currently only has any value as a pulley wheel to allow the smaller alternator to continue to charge the starter battery!

Asked by: Paul Swinney  | 12.22pm, Tuesday 26 April

WW says:

Most alternators on boat engines are effectively car/truck ones- and think how wet/dusty/hot they get in an exposed vehicle engine bay! However, they are generally well ventilated, and this might be an issue, as you suggest.
However, if the engine compartment is too hot, then it can shorten the life of the alternator- also, placing a heavy load on it can make a difference- I wonder if the external alternator controller might have something to do with this? It might be worth trying just a simple zero-loss split diode for a while, to see if that helps.
Forced ventilation shouldn't be needed- there is a rule of thumb that for every 10hp of engine "power" needs 40cm2 of ventilation space for combustion air plus 40cm2 of ventilation space for getting rid of heat.
However, most narrowboats (especially cruiser stern and semi-trad boats, or those with boxed-in engines), have keel cooling tanks and dry exhausts, meaning that the compartment tends to run hotter.
Bringing in the combustion air driectly from a vent by hose, which terminates by the alternator can help keep it cool, without using a fan.
Also, boat alternators tend to have to work harder, for longer, than most automotive alternators- especially if the inbuilt controller is overidden.
It might be worth looking at a different alternator- you should be able to find a comparable one to fit the mountings and the drive belt dimensions. Many Bosch alternators can be fitted to a multitude of brackets, for example.
Sorry that I can't be of more help- perhaps other readers will come up with some further ideas!

Mark Langley  | 5.13PM, Wednesday 27 April

Readers say:

I too have a barrus shire yanmar set up in my boat which is from around the same era.I had domestic alternator trouble from the word go and must have had 3 recon units to date. Eventually i thought i would do the job properly and asked a barrus agent to price me a new alternator. Imagine my shock and horror when the answer came back in excess of £500!!!! Anyway to the point.....tomorrow i am having a conversion carried out by 'FC Marine' who intend to use a brand new 'Prestolite' unit and all the fittings for half of what barrus quoted (fitting included). The guy who is called 'Ed' seemed very positive and states that he has done lots of these giving improved reliability and a slight power increase to boot.
I am pretty upbeat about it and will keep you posted on the result.

Jack Parker  | 7.09PM, Tuesday 24 May

So 'Ed' duly turned up and carried out the conversion which included fitting a brand new Prestolite 90amp alternator (with modified pulley) and also modifying some cables and a relay which he said are potential sources of problems.
Watching Ed work was a real treat. To say he is meticulous does not do him justice but he is so i guess that is that!
It is clear to me now that the mistake i had been making was to persist with the small body alternators such as Mitsubishi or Hitachi which are clearly not up to the job.
My concern was that a bigger alternator would not clear the water cooled exhaust manifold on my engine but Ed showed me that the Prestolite does clear it and fits very neatly.
Once the set up was complete Ed carried out a full test which showed that the unit was charging admirably and with no signs of stress.
Obviously i will have to wait in order to comment on long term reliability but at this stage i am filled with confidence and think that the charging system is in the best condition that it has ever been in thanks to Ed and his expertise.

Jack Parker  | 2.08PM, Wednesday 25 May

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