Replacing Alternator - some help advice needed.

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Hi there,

This is my 1st post on YBW but it certainly won't be my last. I'm in the midst of a complete restore and refit on a 1936 40ft Teak Broads cruiser. I'm starting to refit the boat (needs new eveything) and am starting to think and spec up the electrics.

I'm no electrician but a simple setup should be ok to manage, it's not rocket science and I'm reading up on what I can find.

I want to beef up the alternator charging system. The engine is a straight 6 cylinder diesel Ford 3700e marinised lorry engine.

The current alternator is rated at 35 amp and I wanted to know, if I change the pulley over, can I basically stick any replacement 14v alternator or does it have to be "compatible" e.g. with the starter motor etc.

The current alternator is a Ford 80BB 10300 DB and there is a 90 amp rated Ford Mondeo alternator 92BB-10300-FA on Fleabay for under £50. Can I install this, what are the dangers/issues :eek: if any?

Many many thanks in advance.

Adam.
 

TQA

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Any alternator will do. It does not have to be Ford. The thing to watch is that the pulleys have the same V size and shape and that they are lined up. Use a straight edge on the crankshaft pulley and 1 or 2mm out of line is not a big deal as the belt will cope with that.

Do be aware that if you get over 50 amp alternators the load on the belt is significant and you may have problems with belt wear.
 

FullCircle

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Agree with TQA except in one respect.
Current maximum single belt available for my Yanmar 3YM30 is a Hitachi 80amp.

A tour round the forums at Sailnet or Cruiserforums will tend to agree around that figure as a maximum single belt, but you will suffer heavier belt wear if you have large loads on it all the time.

Best of luck with the resoration.
 

pappaecho

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My Ford Mermaid units are basically the same engine. The alternators fitted to them are 80 amp units, and frankly they never produce anything like 80 amps for more than a few seconds, quickly settling down to a charge rate of 8 -10 amps until the battery banks are fully charged. If you do use the Mondeo or similar alternator make sure they have the same direction of rotation, and V belt pulleys are the same size. Do not worry too much about the debate as to whether the single belt will handle the load, because the Ford Cargo fleet used the engines with 80 amp alternators, and single belts, and they dont seem to have problems.

I would get the new mod bedded in and running before fitting an advanced charge controller, as you may not need it, and that would be £200 which might be better spent elsewhere
 

Playtime

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I would get the new mod bedded in and running before fitting an advanced charge controller, as you may not need it, and that would be £200 which might be better spent elsewhere

It depends if you want your batteries to be 100% charged or only ever a maximum of 80-90%.

If you spend several days at a time away from mains charging, then an advanced alternator regulator is a worthwhile 'investment' IMHO.
 

TrueBlue

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Two points:-

  • I've heard tell (another thread on these fora) that the Stirling unit (and it's not a rubbish unit) can be had for less that £100.
  • Whereas the standard alternator may well work well with s single row belt, if you use a controller - Stirling / Adverc (etc), they will certainly make the alternator work harder and thereby put more load on the belt.
  • You could try a toothed belt (suggest you look at BearingBoys- do a Google), good quality kit and good prices. I've replaced my flat belts with toothed varieties and I've yet to wear one out. Not a huge difference in price and much cheaper anyway than Fenner.


Oh, well it was three points, but the last two were linked..
 
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Thanks all, that has been a great help. It made logical sense that any alternator could be used as long as the rotational direction and pulleys aligned etc.

How can your determine the rotation direction?

I'm currently rebuilding the deck frame and foredeck deckhouse. It's a mammoth project but going well.


Good stuff and many thanks again.
 

PetiteFleur

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  • I've heard tell (another thread on these fora) that the Stirling unit (and it's not a rubbish unit) can be had for less that £100.
  • Whereas the standard alternator may well work well with s single row belt, if you use a controller - Stirling / Adverc (etc), they will certainly make the alternator work harder and thereby put more load on the belt.
  • You could try a toothed belt (suggest you look at BearingBoys- do a Google), good quality kit and good prices. I've replaced my flat belts with toothed varieties and I've yet to wear one out. Not a huge difference in price and much cheaper anyway than Fenner.

The correct type is SPA or SPB Cogged Raw Edge Belts - they transmit more HP than traditional Vee Belts Any local Bearin g/Transmission supplier should be able to oblige - I always used Fenner years ago but not sure if they are still around.
 

Billjratt

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Nobody has mentioned the local scrap (or recycling) yard yet. I got a 60amp bosch alternator for £14. What you need to do is match the mountings and rotation with the original, although the rotation is only the fan behind the pulley, so you can swap if needed.
If your existing alt is old, it may have relays and a clicky regulator outside, while the new one will have everything inside and different connections. Easily changed, but be aware. Also make sure the wiring is up to scratch for the new high current.
Finally, check to see if your original has an isolated negative lead - rather than the automotive method of using the frame, as that is an added complication.
 

TQA

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Agree with TQA except in one respect.
Current maximum single belt available for my Yanmar 3YM30 is a Hitachi 80amp.

A tour round the forums at Sailnet or Cruiserforums will tend to agree around that figure as a maximum single belt, but you will suffer heavier belt wear if you have large loads on it all the time.

Best of luck with the resoration.

Balmar 100 amp alternators come with a single pulley option and a MAX charge regulator. I have one on my boat and it does give the belt some serious stick but with the tension set correctly it does not slip even when I am banging in 100 amps for an hour into my 700 amp hour battery bank.
 

VicMallows

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Nobody has mentioned the local scrap (or recycling) yard yet. I got a 60amp bosch alternator for £14

Pleased to hear the going price has hardly changed in well over 10 years.....must be all those recently scrapped cars.:D

Never ceases to amaze me that people will happily fork out stupid money for such items for the boat on the strange 'better safe than sorry' argument. I'd far rather carry a complete £15 spare unit.

Vic
 
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