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Old 26-02-2016, 17:11   #16
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Re: Alternator Pivot Mount repair suggestions

I'm confused, is the bolt bad or the hole or the casting broke? Assuming your first pic of the oblong hole is the only problem, It seems you can fill that and go on your way forever...?
I'm thinking soft copper tubing hammered into a shape that works...?
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Old 26-02-2016, 17:25   #17
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Re: Alternator Pivot Mount repair suggestions

Bill,

It looks like just excessive loading and the bolt ground its way in. All it takes is a little slop and its off and running. Some more free advice...... I would stay away from any wonder goop like marinetex or epoxy, they usually don't like heat and unless you have access to something like Belzona easy-metal they will not bond or make a loading surface. It looks like that is a 10mm bolt and the amount of wear into the casting is near the same. I would cutoff a piece of bolt 10mm or smaller, unthreaded shoulder portion, that will fit in the hole together with the mounting bolt then use a fender washer on each side of the 10mm bolt to hold captive. As a temp fix.....

On balmar and on some high output setups they will use a pressed steel collar in the casting hole, I would assume this is to aliviate the possibility of what happend to you. It would be a relatively painless retrofit to a new alternator to oversize the hole and press in a piece of SS tubing. A couple small adjustable reemers are good to have around for things like this where you want a fairly exact straight hole.

You may want to bore out the intermidiate piece and go with one single bolt as well, it will be much stiffer.
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Old 26-02-2016, 17:25   #18
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Re: Alternator Pivot Mount repair suggestions

Quote:
Originally Posted by Cheechako View Post
I'm confused, is the bolt bad or the hole or the casting broke? Assuming your first pic of the oblong hole is the only problem, It seems you can fill that and go on your way forever...?
I'm thinking soft copper tubing hammered into a shape that works...?
the bolt has some damage as you can see if you blow up one of the fist two pictures of my last post. Using the same bolt on a new hole would seem to me to allow some play that would threaten the longevity of any temporary repair. There is an auto parts store nearby and I should be able to buy a replacement bolt fairly easily.

The long term solution is to have the entire hole welded shut and redrilled or get a new casting.
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Old 26-02-2016, 18:49   #19
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Re: Alternator Pivot Mount repair suggestions

It's clearly been grinding away for a long time, no question.
The adjuster bracket is what's been holding the alternator in place because that pivot's been loose for a long time too.

If the pivot is just that single, wide (42mm did you say?) lug shown in your first picture then there must have been a hardened & ground sleeve in that hole I think, with a close-fitting bolt.
Wouldn't withstand twisting forces otherwise.

Better IMO design uses two lugs (often as part of a heavy gauge steel bracket bolted to the block) providing widely-spaced pivot points and using a full length bolt.
That way the alternator's supported at its front and rear lugs and twisting is minimised.

With the hinge lug at each end of the alternator supported by its own lug on the block - a single reasonably-well-fitting long bolt works fine even if you forget to tighten it.

If you can arrange a separate support for the rear lug of the alternator you should be able to make a permanent repair.

Might be possible to mount a [-shaped bracket to the 42mm thick lug adjacent to the block and extending back to the rear lug of the alternator.
Can't be sure without seeing it better.
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Old 27-02-2016, 09:04   #20
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Re: Alternator Pivot Mount repair suggestions

I suppose it's a little late, but most likely the reason this happened was because the lower mount wasn't tightened fully after the belt was last tensioned. The lower mount should be very tight, there should be no motion possible. In other words, after you tension the belt correctly, and tighten the lower (engine) mount sufficiently, you should be able to loosen the adjustment arm and the alternator will stay tensioned (but don't run it that way).

As far as fixing it now, if the wallowed out hole is only in the front alternator mount, the best way to fix it would be to disassemble the alternator, get the hole welded up and redrill it. Any of the other 'fill the gap enough to get it into the correct postion' 'solutions' will also work (as long as they don't interfere with the ability to tighten the lower mount as described above), but they will be less permanent.

In way of simplification, if it were me, I'd ditch the two lower bolt system for a single long bolt and nut, by drilling out the spacer for a slip fit of whatever bolt size (10mm?) you have now, enabling you to make sure you have sufficient tension on the lower mount with only two 14 or 15 mm wrenches...
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Old 27-02-2016, 10:10   #21
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Re: Alternator Pivot Mount repair suggestions

Welding a casting of unknown alloy is hit-and-miss at best, it's a load-bearing section of the casting and the mid-point of the hole is 21mm. deep.

Done some tig welding myself, wouldn't even try welding that deep in situ.
On the bench you could probably manage it - but it could still snap across the hole as you drill it. Or next week when it's back on the engine.

I'd make use of that casting's strength by drilling and tapping it so that a steel weldment could be bolted in place forming a new alternator bracket having a better spread of pivot points.
If a mounting point on the block itself can be found for the rear alternator lug so much the better.
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Old 27-02-2016, 10:23   #22
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Re: Alternator Pivot Mount repair suggestions

Yes, cast aluminum welding is an art, the welder better know what he's doing, or it may crack the casting.... depending on the alloy.
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Old 27-02-2016, 10:43   #23
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Re: Alternator Pivot Mount repair suggestions

I like the JB weld approach. If you can get to the auto parts store, they should have some. If not, other cruisers in the Exumas will have some on board. Ride around in the dinghy and ask. Fill the whole hole and drill it out, maybe.

I had recurring problems with alternator mounting bolts on a former boat. After three years, I finally discovered the engine was out of alignment. When the boat was in gear at cruising speed, the engine vibrated, putting a lot of repetitive force on that alternator mount as that heavy alternator swung fore and aft a quarter inch or so. You couldn't really feel it vibrating (at least I didn't).

We came all the way home from the Bahamas once with some Rube Goldberg arrangement where we chocked the alternator in place with some wooden wedges and dowels for an hour at a time, so we could charge the batteries 2-3 times a day.

When we were setting up this arrangement once, I was looking down on the engine from above. We were sailing at a good clip and the transmission was in neutral. As the shaft turned, I would see the engine rocking on its mounts. Mystery solved.

Might want to check your alignment when you get back to repair facilities. Good luck!
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Old 27-02-2016, 12:45   #24
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Re: Alternator Pivot Mount repair suggestions

.395" is a clearance fit for a 10mm bolt. The wear on your lug may have been occasioned by some amatoor using the "next size down", i.e. 3/8" SAE, if procuring the proper diameter bolt seemed to be too much trouble. "For want of a nail, the shoe was lost..."

Fundamental rule of yot maintenance: "Good enuff....ain't!"

IMO the skewing forces acting on the alternator via a tight belt drive would be enuff to damage the lug by "ovalling" the bore because the bolt was a loose fit, and eventually setting up enuff vibration to fracture the metal. You comment about a loud squeak supports the misalingment thesis.

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Old 27-02-2016, 13:38   #25
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Re: Alternator Pivot Mount repair suggestions

I keep going back to this pic and it just doesn't seem like the hole you would expect from wear. Something about it doesn't seem to add up. For one the raised "land" in the middle of the two holes.... with wear you might not expect that.... especially with the sharp corner transition. It almost looks like a machine punched hole. I wonder if it's possible that it was defective from the beginning...? That would be a huge amount of wear... and uniform too. Just thinkin out loud. If there is enough meat, It would be nice to drill the hole bigger and press in a bushing with a larger OD and the right ID. But drilling may not be possible.
I'm not confident JB weld would last long... especially if that hole is actually worn into that condition. It's great stuff and I've used to actually repair a V pulley that lasted for a couple months in that condition, but....
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Old 23-05-2016, 22:17   #26
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Re: Alternator Pivot Mount repair suggestions

Hello, Excellent thread.
I discovered today that I appear to have this exact same problem. I have a yanmar 3jh3e and the bolt hole for the alt. pivot mount has widened to the southwest just as the original posters did. As several noted, the wear area is very smooth, (mine is even smoother) which led me to believe the hole was designed this way.
Since there has been no activity since feb '16 I thought I'd ask if the original poster had solved the problem.
I like the drill larger hole , installing a collar , drilling spacer wider and using one bolt all they way through idea. Do they make collars w/ that much difference between inside and outside diameter? I would have to drill a hole almost 2x wider than the current hole which accepts a 14 mm bolt.
Thanks in advance for any followup.
Will R
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