Need help!!! Lehman 120hp alternator

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Eli27

Senior Member
Joined
Oct 16, 2022
Messages
187
Anybody have any part numbers for an aftermarket alternator for 1979 lehman 120hp engine. I do NOT have a high output alternator which would require a second belt or a serpentine belt kit.

All I'm looking for is a part number that I can give to the part store and hopefully they have it and I can get underway 5hrs ago.

"Your boat is already broken, you just don't know it yet" t

The absolute greatest quote ever
 
In that case you could take the old with you to the parts stores. Most decent counter folks can figure it out or ask the sr guy.
 
I just did this over the summer. Went with Delco 12si units from a local supplier, A1 battery in Quincy, MA.

The adjustment bolt tab location is different, and I ended up changing the adjusting arms for turnbuckle style arms to provide the needed clearance.

If you're in the Boston area, you might check with A1 as he had other options as well.
 
Call Brian at American Diesel. He will have the exact answer for you. 804-435-3107
 
Just take the old one to partsource or similar auto parts store. I replaced mine for 100 bucks canadain (75 US)
The guy at the counter told me it was a standard chevy small block alternator.

I did have to tap into the rectifier to get the signal to run my tachometer. It was a 5 minute job with just a socket wrench and a screwdriver.

you don't need the spark protector on a diesel, but if you want to, you can take the shield off the old alternator and put it on the new one. Mine fit perfectly, but I chose not to put it on.
 
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Call Brian at American Diesel. He will have the exact answer for you. 804-435-3107

All I get is a busy signal all day long, for days on end. Very frustrating when your engine is apart and you need advice
 
Just take the old one to partsource or similar auto parts store. I replaced mine for 100 bucks canadain (75 US)
The guy at the counter told me it was a standard chevy small block alternator.

I did have to tap into the rectifier to get the signal to run my tachometer.

you don't need the spark protector on a diesel, but if you want to, you can take the shield off the old alternator and put it on the new one. Mine fit perfectly, but I chose not to put it on.

Here you go
I still had the box (with the old alternator) in the engine compartment.
Also, FYI, you may have to change the pully if its a different diameter. Just swap it out with the one on the old alternator. Or change the belt. Or make an extension bracket to the alternator attachment if you cant get enough tension on the existing belt. I had to do that with mine because I did not want to go through the hassle of changing to a smaller belt. The current belt on mine is a 46" which was too lose. I made the extension rather than have to drain all the coolant and disconnect the coolant hoses in order to install the a smaller belt ;)
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All I get is a busy signal all day long, for days on end. Very frustrating when your engine is apart and you need advice

Usually Brian is very busy. You have to keep trying. I finally got through after 16 tries within 10min. He's picked up once for me first time trying. The rest (about 10 interactions) have always been hard to get.
 
American Diesel is a great resource but far from the only one, especially if you need answers or parts quick.

There are mamy local mechanics in busy boating areas with decades of Lehman experience, plus rebuilders like Bomac Marine and one in the Seattle area I dont recall.
 
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