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Old 03-02-2013, 17:46   #1
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Will 200 amp alternator work on Lehman 120hp

I am looking at putting a 200 amp alternator on my Lehman 120. Will use or react size double belts etc.. Question is will this adversely effect the water pump or crank shaft with the load ? I have been running a 120 amp alternator or last 6 years and it was fine.
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Old 03-02-2013, 18:08   #2
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Re: Will 200 amp alternator work on Lehman 120hp

Use a double belt, it should be fine. Just get a 40% wrap on the alt pulley.
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Old 03-02-2013, 19:10   #3
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Re: Will 200 amp alternator work on Lehman 120hp

Side loading on the water pump could be an issue. You will need 2 belts or a wide. Me I would set it up as separate from the water pump, so side loading of the water pump was a non issue.
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Old 03-02-2013, 20:01   #4
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Re: Will 200 amp alternator work on Lehman 120hp

Do a serp belt conversion and you will gain tons more belt torque with way less side load issues. and less dust, its why every auto maker has gone to serp belts. The serp belt kits are a grand, maybe scrap this whole plan and get more/any solar. Why run the main? Charging off the main is allmost old tech at this point.
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Old 04-02-2013, 03:14   #5
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Re: Will 200 amp alternator work on Lehman 120hp

Solar is wonderful if your load is small. Kinda gets cumbersome if you are running air conditioning, microwave, electric stove, etc.
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Old 04-02-2013, 03:55   #6
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Re: Will 200 amp alternator work on Lehman 120hp

If you're running air conditioning, microwave, electric stove, etc, then perhaps you should be living in a house, not on a boat.
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Old 04-02-2013, 04:13   #7
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Re: Will 200 amp alternator work on Lehman 120hp

Do you have any battery charging monitoring devices? I just wonder if your current 120 AH is really putting out a full charge for very long or does it taper off quickly down to say 40AH. If so won't a 200 AH alternator just do the same. On a much smaller scale we notice our 60 AH alternator starts at 40AH and then drop quickly down to less than 20 AH, so bigger won't put in any more as the batteries are charged up.

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Old 04-02-2013, 05:04   #8
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Re: Will 200 amp alternator work on Lehman 120hp

Bob, I obtained a double pulley from a truck supplier, carefully drilled mounting holes, and bolted it directly to the static balancer on the crankshaft. 135A Amptec, no problem in 14 yrs.
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Old 04-02-2013, 05:06   #9
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I have several battery monitoring devices, Link battery monitor, Blue Power Panel for Victron multiplus, seperate amp meters for each panel. Old alternator would start at about 110 and drop as expected over time.

200 amp alternator is primarily to support the running of the 40 gal per hour water maker, it uses 19 amps of 110AC, which is inverted out of the battery bank. I have substantial solar (1200W) but having a big alternator could be a big saver on getting the bank back up after making water. Don't plan on using the main engine just for charging, only for when underway. At anchor would be solar or if insufficient running my small generator.

Battery bank is 8 Odyssey 1800 battery's with 214 amp-hrs each. 1700 amp-hrs total.
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Old 04-02-2013, 06:26   #10
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Re: Will 200 amp alternator work on Lehman 120hp

Quote:
Originally Posted by delatbabel View Post
If you're running air conditioning, microwave, electric stove, etc, then perhaps you should be living in a house, not on a boat.
Perhaps. But the fact remains that some folks live on their boats and don't mind paying for the amenities normally found only in a house. If it were not so, genset makers would have a hard time staying in business.
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Old 04-02-2013, 06:27   #11
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Re: Will 200 amp alternator work on Lehman 120hp

Nice, I want your battery bank. Well you've got solar covered, have you thought about a serp belt set up? I really like them, its worlds better than V belts. My westerbeke is super hard on belts, lots of dust and adjusting several times a year. If you look at any make of car and find the year split where they went from 3 or 4 v belts to 1 serp belt the next year the mantaince is 10 times lower, and side loading is reduced greatly. Just a thought, not cheap though. I guess it depends on if you have ever veiwed your belts as a hassle.
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Old 04-02-2013, 06:30   #12
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Re: Will 200 amp alternator work on Lehman 120hp

My tiny boat has A/C. I dont use it much, but if I'm sick of sweating, it's there.
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Old 04-02-2013, 06:43   #13
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Re: Will 200 amp alternator work on Lehman 120hp

Check with Lehman, the dealership or a mechanic that is familiar with doing this. I wouldn't want to make a guess that is wrong and prematurely wear out bearings or burn up belts. Don't assume that all serpentine belts can handle the load.

You might also consider a clutched PTO off the engine for something that is going to draw that amount of horsepower.
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Old 04-02-2013, 07:22   #14
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Re: Will 200 amp alternator work on Lehman 120hp

There are several different widths of serp belts, large trucks and semi's use a wide belt allmost twice as wide as the 2 smaller sizes seen on auto's. This isnt something that could be cobbed together easily, most likely it would be i kit form, made to handle aux. reefer and large frame alternators. So I would assume that it could handle the loads, But asking the manufacture would be obvious.
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Old 05-02-2013, 19:24   #15
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I've looked into serpent belts. Cruisero keeps saying they se coming out with a kit, but have not seen it yet. If you have to manufacture yourself it's kind of pricey. I'll call American Diesel and get a read.
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