Burned out starter and alternator Yanmar 3YM30

dom said:
You're the mechanical whizzo here; I'm just wondering how common defects are in the overrunning gear which isolates the starter cog from the armature as the engine powers up?
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The clutch is a simple centrifugal device very much like the drives on smaller outboards, lawnmowers and even small motorbikes. There is very little to go wrong and the chances are that if it did fill will dirt or rust or wear badly or something then it would fail in the disconnected position rather than the closed position so the starter motor would spin but not turn over the engine.

Richard
 
VicS said:
Its a myth.

If the battery is disconnected / switched off while the engine is running the alternator (diodes) may well be damaged but turning the key to the off position does not do it.

The operating instructions tell you not to turn the key to off while the engine is running because it will disable all the warnings and alarms
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Oh dear. I owe a crew member an apology and several beers.
 
This thread is typical of some of the bow locks talked about on forums.

1 Pre-engaged start motors have a roller clutch to prevent engine driven.
2 Bendix starter motors throw the pinion when the flywheel speed exceeds the start motor.
3 Even if the starter motor was generating at the quoted amps (250 I seem to remember) why should this take the alternator out as the batteries connected to the alternator can be in excess of 250A.

In my experience wrecking a start motor is caused by either key fouled in start position or solenoid fault.
 
I must admit to being wrong. I did not know that the pinion assembly contains an override clutch. A little late in life but I have learnt something new about pre-engaged starter motors.
My thanks to those better informed that have put me right.
 
third engines said:
This thread is typical of some of the bow locks talked about on forums.

1 Pre-engaged start motors have a roller clutch to prevent engine driven.
2 Bendix starter motors throw the pinion when the flywheel speed exceeds the start motor.
3 Even if the starter motor was generating at the quoted amps (250 I seem to remember) why should this take the alternator out as the batteries connected to the alternator can be in excess of 250A.

In my experience wrecking a start motor is caused by either key fouled in start position or solenoid fault.
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Nobody disagrees with that, but it doesn't address the original question which was referring a potential mechanism which could cause a combined starter/alternator failure!

Also what has the Ah (capacity isn't measured in amps) capacity of the battery bank got to do with this problem?
 
"Nobody disagrees with that, but it doesn't address the original question which was referring a potential mechanism which could cause a combined starter/alternator failure!"

Yes, if anyone has definitive thought on that it would be very helpful
 
As an aside, our club ferry has a Yanmar 2gm, at the beginning of the summer the starter started to play up.
We bought a cheap spurious model, which lasted about 6 weeks the casing that held the pinion cracked, some 4 weeks later the replacement broke in the very same place. So a third was put on about 6 weeks ago, that started jamming, needing a bit of a tap to get it going.
I took the old Bosch one to a motor repairer telling him of our problems. He said there was some very poor Latvian, and Hungarian models on the market that are best left alone.
I have now put the original one back on and all seems well.
 
Sprag clutches fail fairly regularly, so I don't think that it can be ruled out completely. It's also an engine which went out of production over twenty years ago and it's in a charter boat (harder use), so whether it's the original starter or a recon unit it probably still has the original clutch in it which has probably not been properly cleaned since it was made.

I think that it would be helpful if the OP had access to the dead starter, but it's probably too late.
 
pugwash01 said:
"Nobody disagrees with that, but it doesn't address the original question which was referring a potential mechanism which could cause a combined starter/alternator failure!"

Yes, if anyone has definitive thought on that it would be very helpful
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Your opening post refers to 'burnt' out and 'fried' starter motor and alternator. I think we've established so far that no user error could have accounted for that. I know it's a (I'm guessing somewhat oldish) charter boat, which you won't (quite rightly) have taken apart. But did you per chance notice blackening around the solenoid part of the starter motor?

Without further investigation one can only guess, but I'm surmising some sort of catastrophic short occurred (possibly in or around the solenoid switch), which managed to fry the solenoid coil and the alternator by shorting the B+ out.

Basically, any and all additional info would help resolve this little conundrum!
 
pugwash01 said:
"Nobody disagrees with that, but it doesn't address the original question which was referring a potential mechanism which could cause a combined starter/alternator failure!"

Yes, if anyone has definitive thought on that it would be very helpful
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The Important fact, with which every one agrees, is that neither of the failures was the result of turning the key to the off position while the engine was running.

A theory which others can debate

A fault with the keyswitch, the solenoid, or the pinion engagement mechanism resulted in the starter motor remaining energised. The starter motor overheated hence the smoke and bunt out. This caused a voltage surge in the electrical system, similar to that which would occur if you turned the battery isolator off. This surge caused the failure of diodes in the alternator ​


Hopefully you did not switch the battery isolator off in panic before stopping the engine, understandable if you did though. If you did don't admit to it
 
Battery definitely not touched...and in fact we don't believe that the key was turned to 0 either.

Thanks everyone for such a helpful set of responses.
 
third engines said:
This thread is typical of some of the bow locks talked about on forums.

1 Pre-engaged start motors have a roller clutch to prevent engine driven.
2 Bendix starter motors throw the pinion when the flywheel speed exceeds the start motor.
3 Even if the starter motor was generating at the quoted amps (250 I seem to remember) why should this take the alternator out as the batteries connected to the alternator can be in excess of 250A.

In my experience wrecking a start motor is caused by either key fouled in start position or solenoid fault.
Click to expand...

The problem with slagging off the responses on a forum is that inevitably one will write something which is, itself, "bow locks".

If you have never seen a bendix starter pinion which is well and truly engaged with the flywheel and is not being thrown back, you haven't lived. :)

Richard
 
I am no mechanical expert.
Just a guy who has done stupid shit. Which seamed like a good idea at the time.
67 MG not a boat.
Among the many irritating little problems enthusiast call character.
My ignition switch failed. the spring was permanently sprung. This was the First time I blew the starter. The key had stayed in the start position. the engine ran fine but that was the end of the starter.
Got a reconditioned starter.
Couldn't find a new ignition switch.
No problemo, I had a cunning plan.
Put an on of switch in the circuit to the starter.
Worked great for a while.
Turn key to on then flik switch to engage starter, moter fires, turn starter off.
Bingo of we go.
Till I forgot to turn starter off.
This required another reconditioned starter motor.
Replaced switch with a spring loaded switch.

Then the solenoid stuck.:)

Alternator survived my efforts and improvisation.:)
 
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Regardless of what the OP did or did not do one would expect that the systems on a charger boat would be idiot proof.
So any failure of stater or alternator would be the problem of the charter company. Do not accept responsibility, just let them try to get you to pay, they have not (should not) have a leg to stand on. Of course if they get ugly name and shame.
olewill
 
I suspect the problem is not a bill to be paid or not. Rather a damage deposit. He would like returned. Without a deduction for new alternators or starters.
 
Burining out starter motors is a well known problem on Yanmar 3YM series; I was told about this by the Sunsail manager/mechanic in Procida, Italy. They have had a number of motors burn out because a small black relay (mounted on the rear of the engine) fails closed, causes the starter motor to remain engaged .... and eventually burns out. [I also have a 3YM30]
I was having another problem whereby my starter would not engage occasionally and these guys were letting me have a spare relay: however they were warning me that it is better to replace the relay (if suspect) because they usually fail closed and cause about 500 euros of damage for a new starter motor. This small relay is not the large relay which is part of the starter motor assembly; unfortunately I do not have my engine manual here with me and cannot tell you the identity of the part (if anyone want to know, I will look it up for them).

I suspect that the starter burning out has somehow caused the alternator to fail ..... not sure how though!
I definitely think that the charter company are taking the pixx and that you should tell them this is a well known problem with Yanmar YM series engines (and possibly other series??).

Turning the key to off will not damage anything as has already been stated.

Alan
 
RichardS said:
The problem with slagging off the responses on a forum is that inevitably one will write something which is, itself, "bow locks".

If you have never seen a bendix starter pinion which is well and truly engaged with the flywheel and is not being thrown back, you haven't lived. :)

Richard
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I agree.
Likewise I have seen a pre-engage starter which not only faied to disengage, but the roller clutch had failed too.

However a possible cause of starter motor failure is overheating it due to long slow starting due to a low battery, caused by a duff alternator....
 
...so a stuck starter relay, stuck key barrel, duff wiring? One way or another this cooks the starter motor, but what about the alternator?
 
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