burnt out alternator ?

[mainbrace]

Help !
Motoring out through chichester harbour this morning engine starts smoking, and horrible grating noise every few minutes. Cut revs right down and idled back to my berth in birdham pool, cut engine and then no sign of electricity on the engine lights. Whilst the engine was running and smoking the charge to the batteries was right down to less than 8 V. Engine itself sounded OK. A few weeks ago I replaced the raw water pump and did not reconnect what I thought was an anode bonding wire which was fixed to a nut holding the pump as the connector broke. What's has gone wrong - is the unfixed wire part of the problem, is my alternator gone for good ??? My boat is old and wooden, I'm fine at fixing the wooden bits but am a complete dunce when it comes to engines and electricity....

 

[Becky]

Where was the smoke coming from? I presume the alternator? If so you would be best off either getting your one re-wound/repaired, a place in Gosport will do that inexpensively. If it is the engine, you will need a man with appropriate skills. I found a really good one over Chi marina way.
If interested pm for details

 

[Robin]

You haven't said what engine or what alternator? If the engine too is old it may have a Dynastart combined dynamo/starter rather than alternator and separate starter. A possibility depending on the noise you described might be the starter motor jammed in mesh. If the wire you didn't reconnect was really an anode wire it would not have made any difference, but it does need to be connected to protect your prop (the engine is connected to the propshaft & prop).

 

[mainbrace]

Smoke didn't appear to be coming from anywhere in particular, just from the engine 'room', but had a distinct electrical smell. Engine was not overheating or loosing oil. The engine is not so old - a perkins 3 cylinder 28HP diesel installed 1995. the alternator is a Lucas A127 55A. I thought the missing wire was for the anode and as the engine is not bonded to the prop leaving it unconnected would not have mattered - could it have been an earth wire associated with the alternator though ? I have not yet taken up the cabin sole to see where it goes.

 

[yoda]

At a guess you have a fairly standard motor car type alternator (I'm sure somebody will correct me if I am wrong) and if it is burnt out sould be relatively inexpensive to part ex. A place in Plymouth knocks them out for about £50 depending on the type. A quick smell of the alternator will tell you if it's been burning and an output of 8v certainly seems to support this. Avoid anywhere that uses the phrase 'Marine' unless you have money to waste.

Yoda

 

[Robin]

Unless you perhaps have a flexible coupling the prop/shaft/engine are all connected by default. The symptoms of noise and electical smell together suggest either starter or alternator and I might lean towards suspecting a starter jammed in mesh and being driven by the engine. Either way you will need a man who knows locally to advise you properly I think.

 

[brianrunyard]

Lucas A127 55A is the same as used on many cars, ifm you need a replacement Halfords would be one source. Suggest you take it off and go to a local auto electricians(yellow pages), they will be able to test it for you and (if necessary) quote for repair.

 

[oldharry]

That doesnt sound like an alternator fault to me.

8 volts was most definitely NOT the output from the alternator. That voltage represents a massive current draw from the batteries, in the order of 3- 400 amps as a result of a major short circuit somewhere, and befoire you start pulling things to pieces you need to go round the electrics and see if you can find the cause of the problem.

You left a wire off the other week? Where is it now? If still attached could it have touched say the starter terminal and activated that - that could account for the grating noises as it tried to engage with a running engine. Or maybe it touched some other live part?

Have a good look round for signs of burning sparking or scorching. It may have blown the alternator diodes which are pretty touchy about that sort of abuse, but I just dont think that was where it all started.

 

[Shanty]

Previous poster's suggestion of starter motor trying to engage sounds possible. If this is what was happening, the smoke might be coming from burning wiring insulation. Well worth examining the wiring runs from the starter motor back to the batteries. Burnt wiring would tend to point to starter motor problems. If you do find this, get the batteries checked, just in case the excessive load has damaged them.

The starter gear will probably have been chewed up by this sort of abuse.

Take the alternator off & get it checked, but don't assume you have found the problem if it is dud.

 

[mainbrace]

Thanks for all the helpful advice - I think I need to see a specialist, the unconnected wire was only the bonding for the anode, and there is no sign of melting etc on any of the wires that I can see, so something else caused it all to blow up ...