Earthed Altenator?

[Ralph]

The alternator on my Yanmar YSE12 is dead and beyond practical repair.

Yanmar want an arm, a leg and several vital organs for a new one.

I went to a trade auto suppliers who have one that will fit which chucks
out 35amps. It however sticks the -ve to earth whereas the original
Hitachi has the neg insulated. Does this matter? It is a third of the
price which is a pretty convincing argument.
Is 35 amps enough?

Ralph Ferrand

Gib'Sea 28
Burnham on Sea Sailing Club

 

[WayneS]

I had a similar situation recently

Can't help with the -ve etc but

If there is a 35amp version, there probably is a 50 amp version. Try callingthe maunfacturer.

The one you have got is not by any chance a VA100 is it?

Cheers

Wayne

 

[Chris_Stannard]

If you have a local Lucas depot they may have reconditioned units, not necessarily Hitachi, or units that can replace your old unit at a more favourable price. It might also be worth trying the lorry spares people as Yanmars are used in trucks and they might carry stocks of aternators, and are likely to be cheaper than the boat engineers.


Chris Stannard

 

[LadyInBed]

Re: Lucas

I also found them very helpful with equivilent parts to replace Yanmar parts (Starter motor). They also gave the alternator a checkover for me.

 

[oldharry]

Re: Lucas

Alternators are pretty tough basically - its only the electronics that are fragile as a rule. have you had it tested out to find out wehat is actually wrong. Any auto electrician (look in yellow pages) will usually do this free and can tell you what has gone wrong.

Im not familiar with the Hitachi specifically, but if there is no ouput then usually it means the electronic voltage controller has failed and shut the output down. Otherwise by far the most common fault is a blown diode which will pass AC to the output terminal - which of course is no use in a DC circuit so the regulator again shuts the output down. These faults are readily diagnosed with the right equipment.

The third most common fault is brush failure - either worn down and no longer making contact, or stuck in their housing. A simple and quick repair.

More rarely the winding have failed - either open circuit or internal partial short circuits.

These faults account for the vast majority of alternator failures, and are easy to sort. Most auto electrical experts nowadays will repalce the unit as a matter of course as it is often the cheapest option, and ensures that the unit supplied is (in theory at least) up to manufacturers specs both mechanically and electrically - in other words there is not another fault just waiting to happen with the consequent hassle and bad publicity for them of having a unit they have repaired fail again. But most of them will repair a non-stock item if it is repairable.

 

[Chris_Stannard]

Re: Lucas

Yes I should have said Lucas rebuilt my old alternator, including replacing bearings, regulator etc, when it had been condemned as scrap. It cost about £130 but was a lot cheaper than the new one the 'expert' considered I needed.

Chris Stannard

 

[jfkal]

I am using the car type as well as a Yanamar Hitachi replacement. It has only D+ and the case is minus and ground. Works fine with me but 35 A is a bit on the low side if you go cruising. Any good alternator shop can repair the old one they never are beyond reppair. One shop said its gone the other did it for 30 pounds. Try to avoid the sharks at the boat yards )

 

[PaulJ]

There is a guy who trades at all the Boat Jumbles in the South who sells Magnetti Marelli alternators for about £40. I bought one off him a couple of years ago, he has (I think) 40 & 70 Amp alternators and is a regular trader so I don't think they are off the back of a lorry! He will almost certainly be at Beaulieu next weekend....

 

[Guest]

While on the subject of alternators, is it possible to get a very large alternator and fix it to the drive shaft of a small marine diesel to make a 12v DC generator. It seems a waste to fit a 230v AC generator when it will mostly be used to run a battery charger. Will a 12 v generator like this and an invertor for use when 230v is required be a more efficient system?

 

[ccscott49]

You can do it, infact theres some people make an alternator especially for this, putting out 12v at about 160 amps. But whether its efficient with an inverter I don't know, however I've seen it done elsewhere.

 

[Ralph]

Re: Lucas

The die-cast housing around the bearing has worn very badly. I suspect that the bearing has ceased in the past. I replaced the bearing but this did no good. I presume the diodes or reg has gone as well as there is no fluence coming out. Because the housing is finished it makes a rebuild impractical. I am quite capable of rebuilding it myself with parts but it's not practical.

Is it normal for the negative side of the battery/alternator circuit to be connected to the body of the engine unit. I am concerned about any electrolytic happenings to the prop and shaft.

I am far too mean to go to boat part purveyors for a new alternator and have already found a good firm in Bristol who are a lot cheaper than Lucus. Most vehicle based kit uses the engine/chassis as an electrical ground at negative potential. I just need to know if it is the same in a marine application.

 

[HaraldS]

Approximately the same efficiency level. A good inverter has a loss of between 5% and 10%. Which is largely made good by the generator part operating at a higher frequency. Normal AC generators work at 50Hz or 60Hz, Alternators with 12 or 14 poles rotating at some 5000 RPM work at over 1000Hz, that allows for making them much smaller and also somewhat more efficient. Even better is to have them run at a much higher voltage.

Some modern gen-sets are doing exactly this, they run higher frequency alternators that output some 400V, that gets rectified and then the 240V 50Hz is generated from this and also 12V and 24V if you need it. Modern semi conductors made all this possible.

 

[halcyon]

Re: Lucas

If the casting has gone, end of story.
Before condeming the unit, has the ign / warning light failed ? if this bulb goes the alternator will not charge, this supplies the initial voltage to the rotor to start the alternator charging. If the battery neg is connected to the engine block, then you can uase a standard car uninsulated unit. Most alternators have a internal link from the rectifier neg to alternator body, and it may be a simple mod to convert to insulatedreturn if needed.