Impeller leaking in L120

[BallardPilot]

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?

 

[psneeld]

thin paper...the thickness of a thin paper bag.

 

[HopCar]

"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.

 

[jleonard]

Inspect the cover and make sure it does not have a scratch were the gasket sits that will be a leak path

 

[C lectric]

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.

 

[BallardPilot]

Thanks, I'll replace the paper seal, The surfaces were clean and smooth. It doesn't leak when running, only after the engine stops.

 

[cappy208]

Are you certain it is coming from the seal? Could be a leaky shaft seal on the other end too.

 

[Marin]

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.

 

[Moonfish]

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...

 

[Marin]

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.

 

[dhmeissner]

Mine came with this:
Welcome to Speedseal Test Reports

I haven't changed the impeller yet, but it's due.

 

[Moonfish]

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!

 

[RT Firefly]

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?

 

[Marin]

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)

 

[RT Firefly]

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?

 

[Marin]

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.

 

[psneeld]

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.

 

[RT Firefly]

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.

 

[HopCar]

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.

 

[capt jerry]

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

 

[Capt.Bill11]

The plug should fit pretty snug in the impeller as I recall so it shouldn't fall out as you put the plate on. I always pack Super Lube gel behind the plug.

The number on the plate is the part number of the plate itself not the whole pump, again as I recall.

 

[HopCar]

Bill, Jabsco pumps have the pump model number on the plate. I don't know about the Johnson pumps that RTF has. That's a good thing to know about Jabsco pumps. With the Jabsco model number you can often buy parts and replacement pumps from a Jabsco dealer much cheaper than you can from the engine dealer.

 

[RT Firefly]

Greetings,
Mr. cj. If you're offering the Jabsco pump to me, thanks but I have a brand new spare Johnson pump somewhere aboard. It's in a safe place along with my stainless steel staples, oak wedges, and a plethora of other "important" stuff I just can't find at the moment (took me 3/4 hour to find my bin of sandpapaer-yup, in the OTHER "safe place). My marina neighbor has a standard comment regarding "safe places-LOB (lost on board).

 

[cappy208]

Any info on the rule of thumb on end space on new impellers and end plates, versus worn in ones? Putting on a new end plate, and I can't recall the info from years ago.

Also, regarding flipping end plates, it rubs off the only numbers you will have to locate a replacement end plate. When flipping it, make sure you write down the numbers and order a new end plate to put into the 'safe place'.

 

[HopCar]

I don't know how you would vary the end space. I just push the impeller all the way in and the paper gasket sets the end space. As the end plate wears, the gap opens and the pump loses suction.

Good advise about recording the numbers when you flip the plate. I usually try to scratch or write it on the worn side of the plate itself.

 

[cappy208]

I can't recall exactly, but I think it was three gaskets on a new plate, two gaskets on the first new impeller, and one gasket on the next then flip of the plate. For three more seasons. The old mechanic I worked with had many idioms like this but I never wrote them down. Age bring what it is makes the recollection more difficult. Actually after discussing this with another engineer the mention of Manila Folder being used first and paper as the plate wears.

 

[Northern Spy]

If the plate has a recess from impeller wear, one could lap it flat with some sandpaper and/or lapping compound.

Probably easier and not too expensive to buy a new one though.

 

[Capt.Bill11]

I can't recall exactly, but I think it was three gaskets on a new plate, two gaskets on the first new impeller, and one gasket on the next then flip of the plate. For three more seasons. The old mechanic I worked with had many idioms like this but I never wrote them down. Age bring what it is makes the recollection more difficult. Actually after discussing this with another engineer the mention of Manila Folder being used first and paper as the plate wears.

A new pump goes with only one gasket installed in it.

 

[sunchaser]

A new pump goes with only one gasket installed in it.

Yes.

Last week when changing impellers (every 18 months/300 hours or less) I asked my favorite mechanic to come aboard and inspect Jabsco pumps for issues going forward. His recommendation - Pumps are approaching 1900 hours, plates are getting worn, rebuilds are iffy and not cost effective, we leave dock for months on end and small ones like ours are a standard throw away item. His thoughts for another trouble free decade - they have one more season in them. BTW this guy replaces about 50 pumps/impellers per season and has been doing it for 30 years on engines big and small. Most Jabscos do use the little rubber spacer, keeps the plate from wearing and grabbing impeller edges.

For those who don't stray far from home and have a get home engine, many run them until they leak. Many but not all.