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Old 19-04-2019, 22:49   #1
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What's this dripping?

Hi,
The engine is a Yanmar2QM20. After installing a new impeller in the water pump">raw water pump there's now a slow drip coming from the slot on the bottom side of the housing. It wasn't leaking before I took it apart, so I'm wondering why it is now.
Any expert advice would be welcome.
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Old 19-04-2019, 23:27   #2
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Re: What's this dripping?

The slot is the tell tale aperture or weep hole of your flexible impeller pump. And the cause is one (or more) worn lip seal(s).

Replacing the lip seal is routine maintenance. And you might as well do it (in future) each time you replace the flexible impeller.

The deal being that around the shaft that turns the flexible impeller there is one (or two) lip seal(s). The lip seals keep sea water from running along the shaft and getting into your engine (where the seawater would mix with your lubrication oil, causing a milky mess that would not lubricate your engine).

And the shaft probably has a slinger washer, whose only function is to sling the water that gets past the lip seal out, so it drips through the tell tale aperture, to alert you to change the lip seal(s).

If you keep running your engine, or even if you leave your engine unused with your boat in the water while that lip seal is leaking, a water film will sit between the lip seal and the stainless steel shaft of your flexible impeller pump. And lead to crevice corrosion that would next cause you to have to replace the shaft too.

So as soon as you see the tell tale drips, you must replace the lip seal.

My tips are therefore:

* pull your flexible impeller pump and change the lip seal(s);

* buy your lip seals at your local supplier of bearings and such like;

* when you buy your lip seals, ask your local supplier of bearings to also supply O-rings of the size to replace the metal garter rings that will be in the lip seals as supplied by them. The O-rings do a slightly better job of providing tension to the lip than the garter rings.

* in future replace lip seals whenever you service the flexible impeller pump. Lip seals are low priced (compared to the cost of repairing the damage that will happen if you don't maintain your lip seals).

See also: http://www.cruisersforum.com/forums/...ml#post2867686
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Old 19-04-2019, 23:38   #3
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Re: What's this dripping?

What Alan said ...
Plus one more thing.
The shaft is most likely corroded or at best has a crust of deposit on it and just a fine line that is clean where the seal used to ride. Your repair has positioned the seal in a slightly different position and caused the seal to leak.
You may get away with polishing the shaft with fine wet and dry emeril, but if it is pitted, replace the shaft ... and the bearings and the seals. Cheap parts.
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Old 19-04-2019, 23:54   #4
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Re: What's this dripping?

Here's an exploded diagram of a fairly generic Yanmar flexible impeller pump (although an older model than your 2QM20).

The object labelled "oil seal" is a lip seal.

"Oil seal" is a functional name: the seal separates oil from water. It could just as legitimately be called a "water seal".

"Lip seal" is a name referring to how the seal works: in this case it's not a face seal (one of two faces that rub together) it's a lip seal (the inner and outer lips contact things to make seals; the inner lip seals against the rotating shaft, the outer lip seals against the body of the pump).

And the object labelled "water seal ring" is what I called the slinger washer.

When disassembling your flexible impeller pump, pay attention to the orientation of the lip seal(s). If the pump has two, one may face to the engine and the other to the impeller. Re-install new ones the same way unless you have expert opinion otherwise.

Question: is the Salish Sea salty or not? I've never been there. And the maps show big rivers leading into it, but a narrow connection with the NE Pacific.
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