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Old 21-07-2016, 11:13   #1
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Yanmar 2012 3ym30x1 alternator

On a friends boat and we had to replace the alternator belt. Finally got the old belt off but can't get the adjusting screw / bolt loose. It seems to be corroded. One alternative is to take the alternator off. It looks like the top bolt should come off and the alternator drop out. Any suggestions? Is that correct? Thanks

Any suggestions to get the adjusting bolt loose? The nut is off.

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Old 21-07-2016, 11:26   #2
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Re: Yanmar 2012 3ym30x1 alternator

I have a different Yanmar, but same type alt mount.

Sounds like you have the lower nut off, correct? That's where the slot is in the arm. The alt should rotate in to facilitate belt replacement. You shouldn't have to remove the bolt, or even the nut to change a belt. Just loosen enough to rotate the alt.

Have you loosened the upper bolt? This is the pivot point for the alt, to push it in and change the belt.

Try loosening some more if you have to. Sometimes it takes a little persuasion to move the alt in. Can be a little stuck from corrosion in the foot mount on top.

PB Blaster is a very good corrosion buster.




Edit to add,...... yes, that long upper bolt is holding the alt on the engine. And the lower bolt adjusts it's position.

Of course you must remove the wires on the back of the alt, with the batteries disconnected first.

I don't think you should have to remove the alt at this time however.
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Old 21-07-2016, 11:31   #3
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Yanmar 2012 3ym30x1 alternator

Yes the alt loosening nut is off. The alt is stuck to the adjusting arm. The very top nut is loose.

We are trying to influence it by using a hammer on a piece of wood on the alternator.

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Old 21-07-2016, 11:39   #4
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Re: Yanmar 2012 3ym30x1 alternator

Wow, that's some serious corrosion then.

Have you tried rotating the bolt to break off corrosion?

Get some pb blaster.

Maybe take the lower adjusting arm bolt on the block out. Wiggle it around.

I think corrosion at the top pivot mount would be more of an issue than the lower arm. It's a long bolt through the mount with a lot of surface area for corrosion to build.

Check the back of the alt for another bracket. You have a different model alt than me. Not certain about what's on the back.
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Old 21-07-2016, 11:41   #5
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Re: Yanmar 2012 3ym30x1 alternator

Thanks, using pb now also. Small problem but can't fix with it stuck. Thanks

It finally broke free. Thanks for your response!


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Old 21-07-2016, 11:45   #6
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Re: Yanmar 2012 3ym30x1 alternator

Careful with the wood block. Should help though.

I would place it on the mount ear behind the lower bracket. That finned case might not withstand much force.

If it feels solid, sounds solid, to a moderate blow. Take a step back. Insure the mounts are truly loose. And no bracket on the back.

Get some pb blaster.
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Old 21-07-2016, 11:47   #7
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Re: Yanmar 2012 3ym30x1 alternator

Quote:
Originally Posted by landonshaw View Post
Thanks, using pb now also. Small problem but can't fix with it stuck. Thanks

It finally broke free. Thanks for your response!


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Excellent!

I think yours was stuck pretty good. But I've seen it before. Especially when one is being careful not to cause collateral damage.

Good job.
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Old 21-07-2016, 12:31   #8
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Re: Yanmar 2012 3ym30x1 alternator

Yes it was stuck. I have though never seen the bolt that is attached to the pivot arm be an all thread bolt. With the bolt being tight, you can take the nut completely off and the alternator is still tight to the arm. You must also unscrew the bolt a little to move the alternator. The bolt was corroded some so we put anti corrosion grease on it. I am afraid that the long bolt that you pointed out could be bad is also. That will be left to another day.

Now back to a drink and sailing tomorrow. Cheers


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Old 23-07-2016, 13:56   #9
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Re: Yanmar 2012 3ym30x1 alternator

I have same engine with a different setup. No long bolt on top, but a 1" bolt on each side, screwing into the engine bracket. BOTH have to be loose for me to swivel the alt.

This corrosion is unfortunately too common on this engine with its weak water pump">raw water pump often dripping salt water all over the engine room, slowly enough to not trigger the bilge pump. By the time it does, the damage is done. Most of my bolt/nuts are rusted, needing an overnight soaking of PH Blaster. I replace them with SS ones and smother them up with Petroleum Jelly.
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