SO 35 Starter Motor Fire

[avrora]

Hi,

I have just been towed in after our second starter motor "fire" in two years. 

It appears to be the case that the starter fails to disengage on our 3YM30 and then runs backwards (?) generating enough heat to melt the HT leads' insulation, causing acrid black smoke but no actual flames so far. To stop the burning I stop the engine. After that there is no possibility of a restart. 

The first time this occurred in a marina, which was very lucky. This time, at sea but a mile off and in 8kts of breeze (also lucky). I don't want a third time. 

Assuming the engineers did as I asked, both starter and solenoid were replaced last time using Yanmar parts. If the forum experts could indulge me I have a couple of questions that my basic schematic reading can't help with:

1.  If I replace the Starter Motor and Solenoid again, and now the ignition switch assembly as well, is there any other aspect to the starting circuit that could be causing this failure?

2.   Does anyone have any better insight into what is actually taking place on my engine? I have searched the boards and there are a few other cases of the motors remaining engaged but no one else appears to have had heat and smoke and the total destruction of an £800 starter.  Am I correct in thinking it's running backwards and generating current?

Thanks in advance for any assistance. Twice is a worrying trend. 

J

[allegria]

Hello Avrora,

How old is your boat/engine? Any mods?
I have a 2010 36i with a 3YM30 and never had any issue like the one you have described.
Have you tried to contact Jeanneau and/or Yanmar?

Sorry to hear that and keep us posted with any findings.

Cheers,
Allegria

[ianqv]

Just a thought....
Check your ring gear for damage on the flywheel. It can be viewed when the starter is removed, just turn the engine over by hand so you get to see all of the gear.

Regards

Ian

[shortarseyoda]

HI there. Really sorry to hear this. We have a SO35 with a 3ym30 and had no issues like this. I don't understand how the starter motor would be able to turn backwards? If it doesn't disengage then it will go forwards. I would suggest then it gets hot as it works as a generator rather than a motor (all dc motors will do this if turned). I would say that the culprit is the ignition switch or any relay or solenoid in the circuit between the momentary position of the ignition switch and the started motor/solenoid. What is happening is that that ciruit is still providing 12v after the ignition key is released to the 'run' position. Does this make sense? Best regards Andy

[avrora]

Sept 15, 2017 6:06:26 GMT ianqv said:

Just a thought....
Check your ring gear for damage on the flywheel. It can be viewed when the starter is removed, just turn the engine over by hand so you get to see all of the gear.

Regards

Ian

This has been suggested to me by a marine engineer who has not seen the boat. I will definitely do this now you've mentioned it as well. 

Are you suggesting the teeth are failing to disengage due to (perhaps) a damaged section?

Thanks. 

[avrora]

Sept 15, 2017 6:23:26 GMT shortarseyoda said:

HI there. Really sorry to hear this. We have a SO35 with a 3ym30 and had no issues like this. I don't understand how the starter motor would be able to turn backwards? If it doesn't disengage then it will go forwards. I would suggest then it gets hot as it works as a generator rather than a motor (all dc motors will do this if turned). I would say that the culprit is the ignition switch or any relay or solenoid in the circuit between the momentary position of the ignition switch and the started motor/solenoid. What is happening is that that ciruit is still providing 12v after the ignition key is released to the 'run' position. Does this make sense? Best regards Andy

Hi Andy,

You're right of course. I didn't think that bit through. It's not going backwards it's doing more of the same.  I think this is what is melting the HT leads though. As you say, it's a generator.  

I now suspect the ignition, which you've picked up on, as it's the only part of the assembly not replaced last time, and, it's the bit most exposed to the environment. 

Can anyone tell me the exact purpose of the solenoid? Is it the same as a start relay, using low current to make an HT circuit live?

j

[avrora]

Sept 15, 2017 1:21:59 GMT allegria said:

Hello Avrora,

How old is your boat/engine? Any mods?
I have a 2010 36i with a 3YM30 and never had any issue like the one you have described.
Have you tried to contact Jeanneau and/or Yanmar?

Sorry to hear that and keep us posted with any findings.

Cheers,
Allegria

Hi Allegra,

She's a 2005, no mods to starting circuit. 

This thread has a couple of similar sounding incidents but perhaps not the damage or proto-fire. 

jeanneau.proboards.com/thread/1673/starter-motor-problems-on-32i

I will certainly report back because although I don't think there's a serious chance of a bad fire, there is *some* chance and losing the engine close to land could be an issue. My windlass doesn't work without the engine so deploying the anchor becomes a trickier and less immediate proposition. 

Most aircraft parts are lifed. It might prove sensible to do the same with certain essential boat parts. I'm thinking ignition, exhaust elbow, impeller etc. 

J

[shortarseyoda]

The solenoid has up to 2 functions depending on the type of starter motor. 1) It's hogh current capable relay to provide power to turn the starter motor. 2) It's an electro-mechanical actuator that on having power applied to it via the ignition switch engages the drive gear of the starter motor onto the ring-gear of the flywheel.

Some designs of starter motor use centrifugal force that engages the drive gear relying on a spring and a helical arrangement on the pinion of the starter motor. However I doubt this is the type used for this application.

You need to check the electrical schematic in the owners manual and replace all componentsin the circuit between the start switch and solenoid. As I say there maybe and additional relay in the circuit, we need to check.

Just FYI Yanmar starter motors are made by Hitachi which are 25% of the price charged by Yanmar.

Kind regards

Andy.

[avrora]

Sept 15, 2017 8:29:30 GMT shortarseyoda said:

The solenoid has up to 2 functions depending on the type of starter motor. 1) It's hogh current capable relay to provide power to turn the starter motor. 2) It's an electro-mechanical actuator that on having power applied to it via the ignition switch engages the drive gear of the starter motor onto the ring-gear of the flywheel.

Some designs of starter motor use centrifugal force that engages the drive gear relying on a spring and a helical arrangement on the pinion of the starter motor. However I doubt this is the type used for this application.

You need to check the electrical schematic in the owners manual and replace all componentsin the circuit between the start switch and solenoid. As I say there maybe and additional relay in the circuit, we need to check.

Just FYI Yanmar starter motors are made by Hitachi which are 25% of the price charged by Yanmar.

Kind regards

Andy.

Hi,

From memory I don't think this is helical/ bendix. I think it is a gear wheel. I will have to check. 


That Hitachi tip will save me £600 if I can get one. Thanks!



J

[Don Reaves]

I have a 2004 SO35 with a Yanmar 3GM30 engine. I recently had to replace my starter motor and solenoid and got this one from jet.com. The cost was amazing, just over $60 US with shipping, using their first-time customer 15% discount. My mechanic said it looked like a high-quality unit, and had nothing bad to say about it compared with the original equipment.

On my SO35, there are no relays between the starter button and the starter/solenoid according to the schematic or a reasonably detailed search of the actual wiring. Like others, I would suspect that the start button got stuck on, causing all your problems.

Don

[ianqv]

Sept 15, 2017 7:54:57 GMT avrora said:

Sept 15, 2017 6:06:26 GMT ianqv said:

Just a thought....
Check your ring gear for damage on the flywheel. It can be viewed when the starter is removed, just turn the engine over by hand so you get to see all of the gear.

Regards

Ian

This has been suggested to me by a marine engineer who has not seen the boat. I will definitely do this now you've mentioned it as well. 

Are you suggesting the teeth are failing to disengage due to (perhaps) a damaged section?

Thanks. 

Yes, this could be one reason.
But as mentioned above... the starter solenoid may be held in by another fault.

This youtube video explains all about starter solenoids and how they work:

Regards

Ian

[mikebz]

That's a nasty experience to have, especially more than once.

If it's current flow which is melting the leads then the starter battery must be 'sinking' that current.  How much current would it take to melt the leads?  Several hundred amps at least, and what would that do to the battery?  I would have thought, at a guess, that the battery would have done something more spectacular than the leads.

[avrora]

Hi,

Thanks so much for all the useful and non-contradictory input. Searching for a  new starter I happened across this PBO thread:

www.ybw.com/forums/showthread.php?464748-Burned-out-starter-and-alternator-Yanmar-3YM30&s=9d0bcdd210097ae667de13cee62ed13c

...which when filtered for noise suggests ignition problems.


When I look at the facts - two separate motors and solenoids do the same thing about 25-30 starts apart, the motor can't be driven by the engine (PBO) and there are lots of people who have had burned-out starters due to ignition failures and finally, it's the only part not replaced on Avrora, it's hard not to conclude that this is where the issue lies. 

I think I am wrong about the motor generating current. I've looked at it today and the most recent incident has not caused melted HT lead insulation although it did before. I am becoming convinced it's simply a case of the switch forcing the motor to keep running until it overheads and burns out. 

Would anyone one like to venture an estimate for how long it would take to do that? Would 2 mins be enough?

I will of course let the board know of any developments. I'm keen for this not to happen to anyone else.

Cheers!

J

PS - somewhere today I saw a "quote" from a Sunsail engineer saying this was a common problem with Yanmar. *If* that's true then this episode may help someone in the future. 

[yfic]

hello, I had the same problem with two starters on my 3YM30. It came from the key getting stuck. a Spanish mechanic solved the problem by adding a Start button.