Perkins 4236 altenator upgrade

barrie169

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Help, Im going to upgrade the altenators on my twin Perkins 4236 desiel setup. At present i have old very 35amp ones with separate rectifiers which leaves me with a mass of wires and a poor charging system.
What i would like is two 70-100 amp ones with built on regulators. I have it seems a choice i can buy lucas marine ones A127 70amp max with insulated earth returns that cost a fortune or hopefully someone on here will give me a cheaper option.
I cant see why insulated earth return is such a big thing, as long as there is a good battery to engine earth strap fitted, does that not mean insulated earth return is not needed?
Also can the two engines and the domestic battery share a common earth this would make life easier as all things would go to a shared earth post.
Now im a bit handy with with fitting stuff and i really want to do this myself two reasons firstly cost and secondly i dont always trust other peoples work.
So if you have any ideas or if some nice person has or would like to draw me a wiring diagram i would be forever grateful and a few beers will be purchased should we ever meet.
Any help or suggestions would be appreciated.
 

bobgosling

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[ QUOTE ]
Insulated return is safer in theory, because a wire breaking loose and touching the engine metalwork wouldn't short out the electrics. This would only apply if your starter motors are also insulated return.

[/ QUOTE ]

Isn't there some galvanic corrosion problem inherent with engine blocks being used for negative earth ?
 

Gumpy

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[ QUOTE ]
Help, .
What i would like is two 70-100 amp ones with built on regulators. I have it seems a choice i can buy lucas marine ones A127 70amp max with insulated earth returns that cost a fortune or hopefully someone on here will give me a cheaper option.


[/ QUOTE ]
Try here
http://tinyurl.com/2goclp
or even better here
http://tinyurl.com/277nn6

I have used one of the two companies but cant remember which one....

Julian
 

brianrunyard

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Unless everthing else on the engine is insulated earth, Starter, Oil gauge sender, temp gauge, Rev counter etc. and the battery negative is not connected to the engine block, there's no advantage in having an insulated earth altenator.
I use a 75 amp one from a Montego, cheap enough from a breakers that I carry a spare.
 

pappaecho

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I dont know the exact total amperage of your battery system, but my single 4108, with a single 35 amp alternator kept 400 amps of both domestic and starter batteries charged without any problems.
recently changed engine to a Beta, which has a 60 amp alternator, and I cannot see any difference in the charge levels of any of the batteries, except possibly the Beta starts instantly, so less drain on the engine battery. My two battery banks have a common negative, so two engines should work the same
 

alan17

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I do not know where you are located but it is very likely that fairly close you will be able to find a company that rebuilds alternators/starters for the motor trade. Speak to them. Give them your old alternator and tell them what you want. They should be able to either match your requirements or at least come very close.
 

SVSirius

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I have a 4236 but it is a 12v system so different specs. I would suggest using external regulators though. Reason being only way to get a real 3 stage unit installed. Most if not all the built ins are simple single stage regulators..

FWIW
 

Chris_Robb

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Get in touch with Adverc - I bought an american 100 amphr alternator (automotive,) with their charging regulator, on my 4236. They are so helpful, they should give you all the answers. here
 

lenseman

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[ QUOTE ]
Help, I’m going to upgrade the alternators on my twin Perkins 4236 diesel setup. At present I have old very 35amp ones with separate rectifiers which leaves me with a mass of wires and a poor charging system.
What I would like is two 70-100 amp ones with built on regulators.

[/ QUOTE ]

What a very interesting topic!

Firstly, I ask myself why you require greater charging capacity. Have you found your batteries keep going flat with the engines running or have you dramatically increased the demand on the batteries?

The new alternators you intend to fit 70-100 Amp will give you up to 200 x 12 watts = 2.4 kilowatts (at 12 volts) which is a huge demand!! I very much doubt whether you have that sort of 12 volt demand on your yacht, I could be wrong?

You could say that this sort of demand is required at start up, maybe? BUT this amount of power going through the fan belts and brackets at start up will put an enormous amount of strain on the fan belt and associated brackets. In the late 1960’s and early 1970’s, I ran a specialist garage which prepared rally cars for International Rallies. At about this time, cars were going from positive earth to negative earth and later the negative earth cars were converted to alternators. The reason for the change +ve to –ve was due to cathodic action and road salts as it was believed at the time that –ve earth cars rusted at a slower rate than +ve earth cars. Europe and American were basically positive with Europe being negative.

Many works teams which were also converting to alternators used EXTERNAL diode/rectifier packs and this was solely due to the heat generated by the alternator under load. It is far easier purchasing diodes at the correct current and cheaper to get them posted out to wherever you live than it will be to obtain a replacement alternator at the same or similar output.

During my time doing alternator conversions, I also saw three failures where the bracket fractured. They was not designed to carry the excess physical loading. Many more times, I also saw UNC bolt holes into the engine block which had become oval and required helicor-ing. Have you ever tried repairing a bolt hole which has become oval? 2,400 watts output might require up to 5,000 input (through the belt and brackets). This is equivalent to over 6¾ horsepower! This is a serious amount of power!

The loading through the fan belt will require it to be kept very tight which places a greater load on the water pump and bearings. Have you considered this point? I always changed the drive belts from ‘V’-belt which is standard to a small 1-inch wide toothed belt not too dissimilar to the common cam-shaft belts of today. Pressing a toothed drive pulley onto new water pumps and alternators are not without problems.

Pulley alignment is a further problem. Alternator upgrades mean that something might be physically larger and therefore possibly/probably out of alignment. If you do upgrade, make very sure the ‘V’-pulleys are directly in line and correct as necessary! If you space the alternator further forward or backwards, you could / will be critically loading the bracket which might cause premature failure! This is due to belt tensioning and resonance from both the alternator and engine or a mix of both. Resonance damping might be required.


[ QUOTE ]
I can’t see why insulated earth return is such a big thing, as long as there is a good battery to engine earth strap fitted, does that not mean insulated earth return is not needed?

[/ QUOTE ]

When they say insulated, do they mean “Insulated” or “Isolated”? [I wonder if they know themselves!].

An alternator is SO simple inside. The only parts to go wrong are:

1) Front bearing (fan belt over loading).
2) Brushes drilling through the slip rings (very common)
3) Brush worn down out brush travels father and faster than inner brush and outer brush becomes open circuit.
4) Diode short or Open Circuit
5) Regulator failure.

I cannot remember ever having a rotor winding fail during use.

[ QUOTE ]
Also can the two engines and the domestic battery share a common earth this would make life easier as all things would go to a shared earth post.

[/ QUOTE ]

The engines and batteries and alternators probably already share a common earth UNLESS you have two separate battery power supplies and charging systems which are totally isolated one from the other. If you only have one set of batteries, you will have a linked common earth.


To summerise:

If you can, keep the diode pack and regulator separate from the alternator due to excessive heat from engine and alternator. Failure is always due to excessive heat >120°C.

DO check your brackets (for fractures), bolts and bolt bolts for ovality as regular maintenance.

To repeat an earlier sentence:

Have you ever tried repairing a bolt hole which has become oval? Have you ever done it at sea whilst the boat is heaving around dead in the water! No thank you!!

Finally, if you do upgrade, make very sure they ‘V’-pulleys are directly in line and correct as necessary!
If you are suffering flat batteries, I suspect a poor installation or battery state and this is what I would service long before I installed new alternators.
 

pvb

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That\'s a bit pessimistic!

Your post is rather pessimistic, and possibly unsettling for anyone who is unsure about larger alternators. As you know, in most circumstances, alternators on leisure boats never run anywhere near full output. However, one of the reasons for fitting higher-output alternators is their ability to deliver a good charge at very low revs. Higher-output alternators also generally have better cooling and are designed for higher reliability. So there are some good reasons for fitting them.

In terms of brackets and belts, there isn't a problem with alternators below say 100A output. A good-quality single V-belt will handle that. And standardisation of mounting geometry means that most higher-output alternators are a straight swap, with no need for alignment adjustments.

You recommend external diode packs; I think that's unnecessarily complicated, and is in any event difficult to source.

With twin engines, another positive reason for specifying higher-output alternators is the built-in redundancy in the event of the failure of one alternator (always assuming the system is appropriately wired).
 

lenseman

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Hi pvb

Thanks for the reply but anyone who is unsure of upgrading needs to know *all* the facts and the pitfalls that can befall them.

The design of the OEM is basically a compromise by the engine (boat manufacturer) and the design limitations should have been considered at that time. Another route to get a higher output at lower engine speeds is to make the alternator pulley smaller which, for a given engine speed at lower revs, will increase the output from the alternator. The regulator will kick in and limit to total power out anyway.

Changing any component whether it is an upgrade or a different component from a different manufacturer ALWAYS necessitates a good long look at alignment and I believe it is correct to draw any prospective DIY person to make a note of these detail.

Much better to be safe than sorry.

From experience, brackets, bolts and belts are rarely inspected routinely or properly and again I was drawing this point to the attention for any inspection.

The boat in question has external diode packs and again I was explaining as to why these are to be preferred and the reasons for external diodes. If you go down the route of replacing external diodes and separate alternator with units using internal diodes then, if and when the diode pack(s) fail, and they do, it is a complete new alternator and as was said by the originator, these are very expensive units. As you can appreciate, shorted cells on the battery bank can cook the diode pack very quickly which would necessitate new alternator(s).

With one alternator failure whilst blue-water cruising, you would still have enough output from the remaining alternator extant to allow passage to a safe haven to effect repairs unless of course you are running a full disco unit and have no regard to energy conservation. Battery volt meter on the battery bank and ammeter(s) in the alternator(s) output line are a very good investment.
 

brianrunyard

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[ QUOTE ]
If you go down the route of replacing external diodes and separate alternator with units using internal diodes then, if and when the diode pack(s) fail, and they do, it is a complete new alternator and as was said by the originator, these are very expensive units.

[/ QUOTE ]

Not true. Diode packs, regulators, brushes and slip rings can all be purchased separately.
 

lenseman

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[ QUOTE ]
Not true. Diode packs, regulators, brushes and slip rings can all be purchased separately.

[/ QUOTE ]

You are totally correct but they are not usually stocked and are unit specific. You HAVE to buy the correct part to make it fit correctly and know exactly what part you require and this is time consuming whereas if the diode pack is separate, you can test and replace with non unit specific parts to 'get you home'.

Plus, as I said in my original post any external diode pack will run cooler and by inference, last longer.

Furthermore, you require ¼-drive socket sets and small Torq-ex or star-drive sockets to even enter these units. I know from a number of years experience how fiddly these units can be to enter and repair.

These tools would need to be purchased to effect a repair and if you went to a marine electronics specialist, he would charge you £n per hour just to strip and inspect whereas you do not need to strip to inspect an external diode pack.

If you were somewhere like down town Port Harcourt near Lagos and you has a diode failure you might be hard pressed to obtain the Part Number xyz/1 whereas you could always 'buy' a diode pack from a scrap Toyota or some such to just to get you going AND OUT OF THERE.

Whilst you are looking for the local Lucas Agent, someone is on board helping themselves to your belongings!!

For any electronic components, an engine, with its inherently high temperatures is a very hostile place and anything that allows them to operate at a lower temperature than their design parameters is a very good thing.

Perhaps the original spec called for external diode for the very simple fact that the heat transfer conducted through the engine block and then into the alternator on that particular setup is just too great and would cause premature failure of the units?

Who ever specified external diode knew what they were talking about.

Finally, if you lump all th parts into one box it is more difficult to diagnose to effect repair.
 

pvb

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Not helpful...

I think you may be well-meaning, but your posts are not at all helpful. You say that "The boat in question has external diode packs" - I don't think it has. I think the original poster said he had "separate rectifiers" when in fact he meant external regulators. This would make more sense on a Perkins engine from the 70s.

There's absolutely no problem at all in fitting say 70A alternators to these engines. No bracket problems. No belt problems. No alignment problems. No diode problems.
 

lenseman

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Thanks for your reply but I will beg to differ. I did not change any part of the originators save for the fact that he stated rectifier pack and I mentioned a diode pack which is exactly the same.

I pointed out the facts coldly and clinically and they are there to be judged, noted and analysed.

It is all to do with risk assessment and when changing anything from the manufacturing norm, you need to be aware and have *all* the different points brought to your attention.

I have not denigrated or in anyway rubbished anyones ideas, I never do. I just point out the salient facts. No guesswork, just facts. I have spend many years repairing alternators and have some considerable knowledge on the subject.

You might not like what I am saying and you *might* have more knowledge that the originator Barrie169 and consider my reply is pessimistic but at least he can note my comments and go forward to any other marine engineer and ask pertinent questions if every the need arises.

If the diode pack. rectifier pack or regulator pack is originally external to the alternator body then you have to ask yourself why? It is invariable a heat problem, nothing more nothing less. Whatever component is out side the main body of the alternator also makes servicing and testing far easier.
 

pvb

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External diodes...

Just in case anyone decides to go down your recommended route of having alternators with separate external diode packs, could you recommend a suitable make/model of alternator?
 

lenseman

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Re: External diodes...

[ QUOTE ]
Just in case anyone decides to go down your recommended route of having alternators with separate external diode packs, could you recommend a suitable make/model of alternator?

[/ QUOTE ]

You are a silly boy and you are acting foolishly by keeping on when you obviously have not read properly what I have said. You are like a bear with a sore head.

Re-read my previous texts and you will see that I am only suggesting the status quo in regards to the originator of this message.

I also stated that to change from OEM has risks which must be addressed. If the alternator fitted to your vessel can have external diodes then fit them externally for the reasons I have mentioned previously.

You are not obviously not an engineer and I may I suggest you leave engineering matters to those that are able capable.

Matter closed.
 
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