So i think i bought the wrong alternator

[pateco]

Decided I was going to upgrade my alternator on my 2GM from 35 amp to 80 amp.
Shopped around online, and thought I found a good deal. Bought this one.

This is my old one.

There is plenty of space for the larger alternator, and it fits the hinge side of the bracket perfectly. The problem is the tension adjustment bracket hits the side of the new alternator before it reaches the tension screw attachment point. Has any found a replacement tension slide that is longer and possibly curved so that I could use this alternator?

Mine looks like this.

I'm thinking a curved one something more like this would work,

 

[mz4wheeler]

The smaller alternators didn't need that curved model. Go to a yanmar dealer with your old bracket, I'm sure they could fix you up. My 2gm20F has the curved bracket.

 

[centerline]

You can usually find the curved tensioner bars at an autoparts store.. always at a performance shop...
if you.have any question as to how it should be wired as opposed to the original equipment, you can call any auto-electric rebuilder and they will be happy to explain it to you...
and you will get much better performance out of the 85amp if you upgrade the wiring on the engine, with an external regulator as well... the oem harness was probably designed for the 35amp alternator.

 

[pateco]

I think its yanmar part number 128990-77330 , but I am not sure, and no one who sells it online has a picture of the part.

 

[Nelsonhow]

If the alt fits and the only problem is that you can't get the belt tight enough, rather than change the adjustment bracket you could try to get a smaller belt. Take the old belt with you and go to any good automotive store that carries a large belt selection and I bet you can get a belt that matches the width and groove but is a little shorter. I'd get a belts 1/2", 1" and 1/1/2" shorter and see what fits, then bring back the ones you don't use. You can also estimate the belt length with a strip of strip paper cut to the width of the old belt and looped around the drive and alternator pulleys. Just mark where the ends overlap, take the paper off and you've got a good estimate of the belt length you need.

 

[Allan12210]

I think its yanmar part number 128990-77330 , but I am not sure, and no one who sells it online has a picture of the part.

Here is a reference from the Yanmar Parts Catalog that shows the curved bracket. The last digits are the same.

 

[Benny17441]

As amps go up belt tension becomes an issue. A longer bracket may induce play, try a shorter belt and see if you can make it work. I agree that 35A today is small but the Yanmar OEM upgrade to 55A is plenty adequate for most needs.

 

[pateco]

If the alt fits and the only problem is that you can't get the belt tight enough, rather than change the adjustment bracket you could try to get a smaller belt.

That's the problem, the new alternator is wide enough that it hits the engine before the bracket lines up. The adjuster bracket needs to be curved and maybe a little longer.

Here is a reference from the Yanmar Parts Catalog that shows the curved bracket. The last digits are the same.

Allan, I was able to find that one (128271-77330) online, the problem is that the S bend in it bends inwards towards the engine, and the one I need bends outwards away from the engine. See pics below

I think this is what 128990-77330 looks like, but I cannot confirm, or find it for sale.

 

[wufibugs]

I too upgraded to an 80 amp alternator. The alternator fit and allows for belt tension adjustment, however the pulley width was 3/8" not the 1/2" required to match the other pulleys. As a temporary fix I used the old pulley until I was able to find a 1/2" pulley that was otherwise identical to the one that came with the new alternator. I want to to keep the 35 amp unit complete and ready as a backup. Surprisingly, the vendor reimbursed me for the cost of the new pulley.

 

[kloudie1]

I think that is a 3GM30 engine. If you get with a dealer or distributor, he can probably look that up for the GM30 .. I don't know who in your area , but I think the distributor is LAborde, 1-800-628-9882 .. Explain to them and the parts guys are savvy enough to know what you are asking for..

 

[Allan12210]

That's unfortunate about the bracket direction. I might be inclined to buy the wrong one and cut it past the bend. Then flip it over and re-weld it. A shop could do it cheaply and it would be plenty strong.

 

[pateco]

That's unfortunate about the bracket direction. I might be inclined to buy the wrong one and cut it past the bend. Then flip it over and re-weld it. A shop could do it cheaply and it would be plenty strong.

Allan, I have been able to find yanmar part number 128990-77330 online at one or 2 locations, but none of them have pictures of the part itself on their site, so I cannot confirm that it is the right one.

 

[Ericson27]

Hi there,

Were you able to find a solution? I've just been given a 55amp Hitachi for my Yanmar 2GMF and am having the same issue. I was able to find a picture in a parts catalogue of the bracket you posted. It is from a 3YM30. Was that the fix?

Thanks

 

[pateco]

Hi there,

Were you able to find a solution? I've just been given a 55amp Hitachi for my Yanmar 2GMF and am having the same issue. I was able to find a picture in a parts catalogue of the bracket you posted. It is from a 3YM30. Was that the fix?

Thanks

I have the new part at home, but have not tried it on the boat yet. Time and wet weather have been an issue recently. I don't remember the part number I ordered, I am pretty sure it was 128990-77330, but I can check when I get home. It looks like it should work perfectly, but I won't know until I try it out.

 

[Ericson27]

That's great. I'm not in a big rush to get mine done so I'll wait to hear about your experience before ordering one myself.

 

[alexco38]

Made one, easy enough.

 

[Capt jgw]

I bought the heavy duty tension bracket from Balmar when the home made one on my engine broke. 1/4" thick so its sure strong enough. No bends in it though, I chucked it in a big vice and beat it into shape. I didn't think of the auto performance shop, no doubt would have been cheaper.

 

[druid]

My experience with Yanmar is that the part you need (alternator bracket) would cost $250 from Yanmar or $30 from an auto-supply place (or maybe $80 custom-made).

druid

 

[Ericson27]

I looked for one at wreckers yards and couldn't find anything. The brackets from Yanmar are surprisingly cheap. $15-20. The issue is finding the right one.

 

[Ron20324]

[QUOTE.... Time and wet weather have been an issue recently. ....[/QUOTE]
Oh, FINALLY... someone from the sunny south complaining about the weather ! Now you know how us Yankees feel when the white sky decides to dump on us- like tomorrow?