BMC Alternator

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nashynetfit

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Dear Forum,

I have a diesel engine BMC 2.5 as far as I have been told and after having an electrical engineer look at the boat, he has advised to get a new alternator as the current one is knackered.

I can read that the old one is a Lucas, but there are no other serial numbers etc, and was wondering if anyone can let me know what alternator would fit this engine.

Many thanks
 
does it have a black plastic back, a thick and a thin wire?


It's a Lucas ACR....

Internal reggy- just connect thick wire to battery and thi to warning light (switched)

Nick

and welcome to the Forum!
 
Looking at ordering new alternator via ebay as where I live Epsom, there asking £40 just to test alternator and there doesnt seem to be anywhere local that stocks what I may need.
 
You could just take it to a breaker's yard and get a modern one that will fit the mountings. A modern one will have higher output at low RPM probably.
I got a mondeo one for £25 and fitted it to a Yanmar with a few spacers.
 
nashynetfit said:
Looking at ordering new alternator via ebay as where I live Epsom, there asking £40 just to test alternator and there doesnt seem to be anywhere local that stocks what I may need.
Click to expand...

It is almost certainly a Lucas alternator. Do a search on Yellow Pages and find a reconditioner - as already suggested there is usually one locally. Unlikely to be anything specifically marine about it.
 
Lucas ACR covers a range of sizes IIRC.

Also very easy to repair yourself.

I had one which at different times needed:

new brushes .. local shop had those
new rectifier .. by chance I already had one
new regulator.. the motoring club at work got that for me. Ordered first thing and on site by lunchtime.
new slip rings .. ditto
 
I also have a BMC engine, although mine is a 2.2. The alternator it came with is the old one with an external regulator, output is fairly low. I bought a new one from Chertsey Marine, who also supplied the brackets it needs, as the later alternators are a good deal smaller than the old ones. Many canal boats use these engines and parts are fairly readily available. I had a small problem obtaining longer bolts for the new front end brackets, which attach to the chain case. Bolts that screw into the block are 5/16 UNC but those that pass through with a nut on the back are 5/16 BSF. I bought both on EBay.
 
The one on our BMC is a Lucas type as well. The engine spec says it will be a 16acr, 18acr or 17acr-m........no idea what all that means though!
We are looking to change ours though as it does not have a tacho output so will probably take it to a scrappy and get a modern one with the tacho output and check the mounting brackets are the same(ish) size.....spacers and/or different nuts and bolts may be required.
 
Electrical engineer

nashynetfit said:
Dear Forum,

I have a diesel engine BMC 2.5 as far as I have been told and after having an electrical engineer look at the boat, he has advised to get a new alternator as the current one is knackered.

I can read that the old one is a Lucas, but there are no other serial numbers etc, and was wondering if anyone can let me know what alternator would fit this engine.

Many thanks
Click to expand...

I wouldn't be so impressed with your "electrical engineer." To describe an alternator as "Knackered " means he has no idea and hopes a new one will fix the problem. As you can see from posts sure it might be more economical to replace it but on the other hand an alternator can always be fixed. They are quite simple and reliable. Indeed your problem may well be wiring anyway. good luck olewill
 
William_H said:
I wouldn't be so impressed with your "electrical engineer." To describe an alternator as "Knackered " means he has no idea and hopes a new one will fix the problem. As you can see from posts sure it might be more economical to replace it but on the other hand an alternator can always be fixed. They are quite simple and reliable. Indeed your problem may well be wiring anyway. good luck olewill
Click to expand...
Thanks William, The guy was very helpful and explained that there was no field due to the light staying on. All the connections on the boat wiring have been changed and solded and hopefully with a new alternator I can take the boat out for the first time in a year of owning it, as its had a lot of work.

I know I can buy a second hand one from a scrap yard, but would you know if I brought a new lucas 17acr would these have the higher output, was thinking of one that has 45amp

Regards
 
nashynetfit said:
Thanks William, The guy was very helpful and explained that there was no field due to the light staying on. All the connections on the boat wiring have been changed and solded and hopefully with a new alternator I can take the boat out for the first time in a year of owning it, as its had a lot of work.

I know I can buy a second hand one from a scrap yard, but would you know if I brought a new lucas 17acr would these have the higher output, was thinking of one that has 45amp

Regards
Click to expand...

A bit of Googling comes up with increasing current ratings for the ACR 15,16,17 and 18. 18 ACR being 43 amps.

The one I refererred to earlier was an 18ACR on a BL/Rover 2200
 
nashynetfit said:
Dear Forum,

I have a diesel engine BMC 2.5 as far as I have been told and after having an electrical engineer look at the boat, he has advised to get a new alternator as the current one is knackered.

I can read that the old one is a Lucas, but there are no other serial numbers etc, and was wondering if anyone can let me know what alternator would fit this engine.

Many thanks
Click to expand...

11 ac type will have a 4 wire seperate regulator.

More likely to be an ACR type with an internal regulator. 16 ACR 34 amps 17 18 up to 20 ACR 66amp.

All ACR types usually fit as they came with a sliding bush in one mounting hole.

A used one fitted with a set of new brushes would be my choice.
 
Alternator current rating

You must bear in mind that a higher current rated alternator will not necessarily improve your charge current.
Assuming a simple one battery system or even 2 ordinary sized batteries with parallel connection. The charge current depends on what the batteries take at 14v regulator voltage. That depends on battery size and charge state.
The current rating of the alternator is only a limiting factor and almost always you will be charging at far less than the current rating of the alternator. So unless you want to run huge loads ie a large inverter with engine running then the current supplied by alternator will be mostly far less than 20 amps. Sure a bigger alternator might run cooler at extreme load but that is about all the value of a bigger alternator unless you get into fast/smart charging of big batteries.
So a bigger alternator is like buying a Ferrari in Singapore. Traffic jams mean you can never exceed walking pace anyway. olewill
 
Many thanks for all your help, I purchased a new one yesturday that is a modern version of the 18acr, that produced close to 60 amp for £44 including delivery, so very happy with that.

I'm sure I'll be back again as you have all been so helpful
 
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