Upgraded alternator keeps getting loose

[Puget Dan]

I upgraded the alternator on our 45 horse Lugger diesel engine to 100 amp Balmar and it works well except keeping the belt tight has been a problem. It the alternator bolt keeps loosening after 3-4 hours running the engine. I have added a locking washer, any other suggestions?

[Jubilee39]

If you are still using a single pulley that is too much power drawn and probably stretching the belt. Typically a v-belt is good for about1/2 hp. A 100 amp alternator can use 1hp or more depending on amperage and voltage. Add a second pulley and you will be better off. Do you have much black dust around your install.

[wellin]

Locktite the threads.

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[DeepFrz]

If your alternator mounts are okay and the right size and your locking bolt is the correct size then try Nord-Lock lock washers.
Nord-Lock wedge-locking washers | Secure your critical bolted joints with the original lock washer from the bolting experts

If you are using a Balmar external regulator then you could use the belt manager to set the max alternator output down about 10-20%.

[Stu Jackson]

Get a much longer bolt and put a nut at the back end with a lock washer, too.

[svJasmine]

Too much alternator for 1 belt. I would guess that the bolt isn't loosening, but the belt is stretching.

Green stripe belts will help.

[Cadence]

Originally Posted by Puget Dan

I upgraded the alternator on our 45 horse Lugger diesel engine to 100 amp Balmar and it works well except keeping the belt tight has been a problem. It the alternator bolt keeps loosening after 3-4 hours running the engine. I have added a locking washer, any other suggestions?

Check you aren't over tightening the belt.

[sy_gilana]

+1 too much power for one belt.

[DeepFrz]

Do we know what kind of belt it is? I looked at some pictures of small Luggers and they had flat belts. The OP hasn't said what kind of belt he is using.

[jeepdoesrubicon]

Upgrade the belt to serpentine. I know, you will have to change all the pulleys. Also use red loctite to secure all the bolts.

Paul

[Kerry1]

Don't know if this will be on topic but I had a problem with loading up the belts sufficiently while I did the retaining bolt up to keep belts tight. Not a lot of room and need to be built like an octopus to keep everything tight while doing bolt up. I ended up making a modification which involves a small stainless rigging screw to hold the tension on belts temporarily and then have hands free to tension bolt. I will add photos to illustrate shortly.

Another thing I learned after burning out the alternator was to consider battery condition before deciding to blast the cobwebs out of the engine by running at max power for a while. I understand all diesels should be worked hard at least for a while to keep piston rings exercised. I did this when my batteries were particularly low and in poor condition, and the added load on the alternator caused it to burn out. A lot of foul smelling smoke ensued. If I had ran motor at cruising speed until batteries were more charged, and then ran at max, I think I might have saved the alternator.

[btrayfors]

A 3/8" V-belt (like a Gates Green Stripe) will handle a 100-amp Balmar just fine. I have one and have worked on lots of others. They must be installed correctly, aligned perfectly, and tensioned appropriately.

As noted, an external regulator such as the Balmar MC-612 or MC-614 can be set so as to de-rate the output of the alternator. Balmar calls this the "belt-saver" mode.

After installation of a new belt there is some belt stretch, of course. Re-adjustment after a few hours use normally will take care of that.

Be careful if you see any black dust about....that's a good indication of misalignment of the belt.

On my own boat several years ago, the 41" 3/8" V-belt on my 4-108 driving the water pump and the 100-amp Balmar alternator kept coming loose. I had to tighten if very often. Finally, after close inspection with good lighting, I found that the adjusting arm itself was not well secured to the engine block, and was slipping. Fixed that, and fixed the problem.

Bill

[svJasmine]

alignment can be the problem. The best belts are also important. I have used lesser belts and had problems.

aligning belts

http://www.gates.com/~/media/Files/G...0Alignment.pdf

[Delmo]

I run a Bosch 120amp alternator with single pulley and a green stripe belt. Works fine but, initially, did have a tendency to loosen. I read about a system of installing a turnbuckle attached to the alternator so thought I'd give it a go. I installed a s/s turnbuckle and connections to a strong point adjacent to the alternator, tensioned the alternator belt to the requisite tension and then locked off the turnbuckle. Works fine - no slippage or loosening.

[wsmurdoch]

Originally Posted by Jubilee39

If you are still using a single pulley that is too much power drawn and probably stretching the belt. Typically a v-belt is good for about1/2 hp. A 100 amp alternator can use 1hp or more depending on amperage and voltage. Add a second pulley and you will be better off. Do you have much black dust around your install.

100A output x 14V into battery = 1400W

If the alternator is 90% efficient (they do get hot) it would require 1400W/.90 = 1556W to drive the alternator.

1556W / 746W/HP = 2.086 HP

Do you see black dust in the engine compartment when you charge heavily into your batteries especially at low engine speed... like when at anchor. For the same horsepower carried by the belt, the tension in the belt is greater the slower the belt speed. High tensions lead to slippage.

If you shut off the engine and then quickly touch the belt, is it really hot... it is slipping, that made the dust.

With the engine off touch the alternator belt... is your finger black? Dusting the belt wears the belt away resulting in the belt riding lower in the pulleys and the belt becoming loose. It does not take much wear to loosen the belt, and a loose belt slips more, so this just cascades.