[Jon Fitch]

If you can fit a smaller pulley without over speeding the alternators, that’s probably the easiest/cheapest route. I’ve run out of time to chase this but I think my ultimate solution involves a hair pin stator alternator, either Balmar’s or someone else’s. The Delco 24 and 28 are similar to the hair pin style.

[Jon Fitch]

Not what I’m talking about, that is the tension idler. It doesn’t care what alternator is on there. The tension arm I’m talking about is the one that in the old days had a slot to set the belt tension. Now it’s just another arm to hold the alternator on.

[Jon Fitch]

That’s remote oil filter.

Also, is there a tension arm that works with the QSB and 28si alternator? I had to fabricate one for the Balmar and could do it again, but it was a pain to do on the boat away from my machine shop.

[Jon Fitch]

Will the 28si fit on an early QSB? It looks like I’d have to swap the alternator mount to the J180 and also remove the remove oil filter as the lines are very close to the original small alternator.

[Jon Fitch]

Hmm, tried to post a reply but it won’t let me. The alternator is a Balmar 94-12-210-IG. I’ve spent the money but if another could be found with similar specs but higher low speed output (that will fit!) I’d consider it. The engine draw exceeds the output by itself, so the DC architecture of the boat is irrelevant.

According to the published Cummins specs, a number of the 6BT and 6BTA engines idle at 700 or 750.

What’s the magic of the 600 rpm idle? The engine idles smoother a little faster, in my boat and others. I normally throttle up a little with the transmission locked out for that reason, but it isn’t practical to do when maneuvering.

[Jon Fitch]

It is a Balmar 94 series alternator and Balmar 614 regulator. I could find no other alternator that would fit the space available without very substantial modifications. It should be noted that Cummins requires an offset pulley with limits the choices somewhat.

[Jon Fitch]

Thanks for the suggestions, but everything has been checked, all works as it is supposed to. A larger pulley will overspeed the alternator at full rpm. I just want to change the idle and I am astonished at how hard this is proving to be.

[Jon Fitch]

Nothing wrong with the alternator. It is a large frame high output and they put out less at idle. Since a 6BTA engine idles at 700 I don’t think I’ll have any more trouble than they do.

I’m pretty amazed at how hard it has been to find out the answer to this seemly simple question.

[Author]

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