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Old 09-28-2014, 04:29 AM   #1
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Impeller leaking in L120

I recently did fall maintenance on my Chub, after replacing the impeller, the plate that seals in the impeller is leaking a little. I used the fiber seal, as the previous owner has good luck with those. I've heard that those seals tend to leak a bit then seal better after a few hours of running and a re-torquing.

I am curious if anyone has found a better seal or can confirm that the fiber seal will expand/seal further. I've heard guys that use grease, rubber seals, etc. What works for you Lehman experts out there?
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Old 09-28-2014, 07:29 AM   #2
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thin paper...the thickness of a thin paper bag.
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Old 09-28-2014, 10:57 PM   #3
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"I've heard that those seals tend to leak a bit then seal better after a few hours of running and a re-torqueing"

No, it shouldn't leak at all. Try tightening the screws. If that doesn't stop it, replace the paper gasket with a new one. You may have damaged it when you installed it. Also check that the gasketed surfaces are smooth.

Like PS says you can use thin paper as an emergency gasket but you should be able to get a factory gasket pretty easy.
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Old 09-29-2014, 07:34 AM   #4
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Inspect the cover and make sure it does not have a scratch were the gasket sits that will be a leak path
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Old 10-01-2014, 12:41 AM   #5
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Check BOTH the sealing faces on the cover and the pump body for dings, scratches.
Use a small stone to remove problems. One of the combination 2" x 8" stones with different grits on each side and a bit of light oil will work wonders.
Just remove the marks. Don't start removing a bunch of metal past what is neccesary.
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Old 10-02-2014, 03:33 PM   #6
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Thanks, I'll replace the paper seal, The surfaces were clean and smooth. It doesn't leak when running, only after the engine stops.
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Old 10-02-2014, 04:15 PM   #7
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Are you certain it is coming from the seal? Could be a leaky shaft seal on the other end too.
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Old 10-02-2014, 05:11 PM   #8
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I am curious if anyone has found a better seal or can confirm that the fiber seal will expand/seal further. I've heard guys that use grease, rubber seals, etc. What works for you Lehman experts out there?
We replaced the stock Jabsco/Lehman water pump/drive coupler with a new Johnson pump on both of our FL120s. We use Johnson impellers in these pumps.

Before we made this change to our engines, we used the Jabsco impeller that was called out for the Jabsco pumps that were on the engines.

When I change impellers, I always use a new cover gasket (the paper one that comes with the new impeller) and I always grease it on both sides before installation.

We never had leaks from the covers of the Jabsco pumps, and we've had no cover plate leaks from the Johnson pumps. We did have leaks from the rear of the Jabsco pumps when the shaft seals wore out.
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Old 10-02-2014, 09:29 PM   #9
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Replaced mine with the paper cover gasket that came with the new impeller and greased both sides (also making sure the cover and pump housing were clean and smooth). Now they "sweat heavily". I have watched them both for many minutes underway and did not see a single drop. But when running my finger under the cover/gasket/pump housing, it comes up wet...
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Old 10-02-2014, 09:50 PM   #10
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Perhaps this is due to having very cold water running through a metal housing that is in a very humid environment and a hot one at that. The humidity can be taken even higher if there is any water in the bilge that the heat in the engine room can be evaporating. The cold metal of the pump housing is condensing the moisture out of the air in the engine room.
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Old 10-02-2014, 09:56 PM   #11
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Mine came with this:
Welcome to Speedseal Test Reports

I haven't changed the impeller yet, but it's due.
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Old 10-02-2014, 11:58 PM   #12
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Perhaps this is due to having very cold water running through a metal housing that is in a very humid environment and a hot one at that. The humidity can be taken even higher if there is any water in the bilge that the heat in the engine room can be evaporating. The cold metal of the pump housing is condensing the moisture out of the air in the engine room.
I like that explanation!
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Old 02-04-2015, 07:09 PM   #13
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Greetings,
Changing impellers and yes, I'm chasing broken off blades. The cover plate is worn (upwards of .008" in places). Is it possible to simply flip the plate over? The old impeller didn't have the central rubber "plug" installed. Is this super critical?
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Old 02-04-2015, 07:53 PM   #14
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RTF--- If your FL120 has the stock raw water pump system on it consisting of a Jabsco impeller pump and the Lehman drive coupler between it and the accessory case on the front of the engine, yes you can simply flip the impeller chamber cover plate over and carry on. This is a "mechanic's trick" I was taught by our diesel shop not long after we got our boat 16 years ago.

BTW, the impeller does not care about the Jabsco engraved data on the center of the outside of the cover plate when you flip the plate.

I did this on both our raw water pumps as both plates were worn down some on the inside. As you know, the wear is like reducing the compression of an engine. The more wear on the inside of the cover plate the more water slips past the edges of the impeller and the volume and flow rate through the system is reduced.

We have long since replaced both our stock raw water pump/drive couplers with new one-piece Johnson pumps. I believe the cover plate on the Johnson pump is symetrical as well so it could probably be flipped, too, when the inside wore down enough to warrant it. (photo)
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Old 02-04-2015, 08:01 PM   #15
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Greetings,
Mr. Marin. Thanks. Johnson pumps on both sides. I'll give the "outside" a quick swipe with some emery cloth just to make sure there are no nicks to impede sealing c/w supplied paper gasket. And the rubber plug that fits into the center of the impeller?
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Old 02-04-2015, 08:40 PM   #16
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And the rubber plug that fits into the center of the impeller?
That one I can't help you with. The impellers we use in our Johnsons don't have this, or if it's there it's not something I have to put in. I simply remove the new impeller from it's child-proof, thief-proof, tornado-proof, thermo-nuclear device-proof packaging, soap it up with Lemon Joy, stick it in the pump, and put the cover plate back on.

We use Johnson impellers that we get from our diesel shop. I'm not familiar with any other kind.

I will hazard a guess that the center plug is not critical as long as the impeller blades and the outer rim of the central impeller body make tight contact with the inside of the impeller chamber. But it's just a guess and if you're at all in doubt I'd ask someone who knows more about these pumps than I do.
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Old 02-04-2015, 08:52 PM   #17
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I've seen it go both ways with those plugs....most engines I have worked on supply the plug...but my pumps never needed them.

Did the one that came out have one? If so I would use it...but I will bet it may not matter.
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Old 02-04-2015, 09:02 PM   #18
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Greetings,
Mr. ps. Nope, old impeller didn't have one but replacement "kit" does. The way the plate is worn suggests addition of the plug may minimize groove development But the washer/dryer is in the way so I may need 5 hands and 4 elbow joints to hold the whole schmutz in place to get a couple of screws started. So, the plug may stay out. The Admiral wants to keep the washer and dryer but it's MY engine room or so I'd like to think...I'd just as soon dump them and put in another nice workbench.
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Old 02-04-2015, 09:20 PM   #19
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I'd love to start an argument with Marin and PS because it's so fun, but I agree with them. The only thing I can add is to record the model number of the pump if it's on the plate you're going to flip.
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Old 02-04-2015, 09:31 PM   #20
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I'd love to start an argument with Marin and PS because it's so fun, but I agree with them. The only thing I can add is to record the model number of the pump if it's on the plate you're going to flip.
i have a used 120 pump that you can rebuild for sale for 50.00$ plus shipping, it is a jabsco
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