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Old 05-22-2010, 04:06 AM   #1
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120hp Lehman Raw Water Pump

Can anyone please tell me the size of the raw water pump onthe 120hp lehman
And the impeller size


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Old 05-22-2010, 05:00 AM   #2
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RE: 120hp Lehman Raw Water Pump

its a 5850-0000 i belive. call american diesel they have everything lehman at the best price. 18044353107

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Old 05-24-2010, 10:28 AM   #3
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RE: 120hp Lehman Raw Water Pump

Be aware that the stock raw water pump on an FL120 is not a very good design. The Jabsco pump itself is okay--- they can be overhauled and are still available new. The problem is the Lehman-designed drive coupler, the component that plugs into the engine's accessory drive and in turn drives the pump. As designed it has a "fatal flaw" that will eventually cause the drive unit to fail.

As these drive units are no longer available, and repairing them is a temporary fix at best, the solution is to get rid of the whole assembly and replace it with a new Johnson pump. This is something Bob and Brian Smith at American Diesel highly recommend. Bob did much of the original marinzation work at Lehman and designed the pump drive coupler which he admits today is a less-than-ideal design-- in fact he told me it was the only component of the Ford Lehman engine to ever have a factory recall.

If one replaces the original Jabsco/Lehman setup, the FL120 is normally fitted with the 3/4" Johnson pump while the higher flow volume 1" pump is what is fitted to the FL135. However the 1" pump fits just fine on an FL120 which is what we had installed on our two engines. We kept one of the old Jabsco pumps and the Lehman drive unit that wasn't failing as a spare.
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Old 05-24-2010, 11:14 PM   #4
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RE: 120hp Lehman Raw Water Pump

Interesting about the 1" vs 3/4". I had Boat US out of Reidville, VA pick up a pump from Brian last year which I changed out in the middle of the night while being towed across the Chesapeake due to the very failure you mention. Would have liked to have gotten the 1" pump however.
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Old 05-25-2010, 12:24 AM   #5
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120hp Lehman Raw Water Pump

We just lucked into the knowledge. When an examination of a pump we had in*for a leaking seal/worn shaft showed that the shaft of the Lehman*drive coupler was cracked and was well on its way to a sudden failure, the recommendation of our diesel shop was to change both engines to Johnson pumps. As it turned out, the 3/4" pumps were back ordered, but the shop we use (and American Diesel who they get their pumps from) said that we could go with the 1" pumps instead, which had the advantage of the higher flow volume.

Where I noticed this in particular was the temperatures of the transmissions. The engine temps on the gauges was unchanged, but the "by feel" temperatures on the transmissions were noticeably lower. They never ran so hot that you couldn't comfortably keep your hand on them but with the 1" pumps they ran noticably cooler, which with a tranmission is always a good thing, I think.

-- Edited by Marin on Tuesday 25th of May 2010 01:40:59 AM
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