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