The shaft in this pump tends to wear an oblong hole in the bushing. This is due to the constant side load imparted to the shaft by the rubber impeller running in the non-symmetrical bore. The worn bushing allows shaft runout, i.e. the shaft isn't centered as it goes through the rubber oil seal. This eventually wears the seal lips enough such that water migrates past the seal. The symptom is water dripping out of the weep hole in the pump body especially when the engine is running. If there were no weep holes the water could potentially migrate all the way into the engine block and contaminate the oil.
The pump can be rebuilt for about $45 worth of parts: a graphite bushing and two oil seals. The graphite bushing, referred to as a "carbon" bushing in the original documentation, is available through eBay and other web destinations under Sherwood part #11519. The bushing is 0.875 inch O.D., 0.625 inch I.D., and 1.250 inches long.
From experience, standard bronze bushings tend to wear oblong in one season. This one is an example.
This is the casting with the old bushing pressed out, cleaned up, and ready for new bushing and seals.
The graphite bushing can be pressed into the casting using an arbor press or by pressing it between the jaws of a large vise. An appropriate wrench socket makes a good press tool. The bushing presses in rather easily. Make sure the force is applied axially, i.e. not at an angle. Although the words "graphite" or "carbon" make the bushing sound soft and vulnerable, the bushing material is reasonably tough. The I.D. remains unchanged after pressing and does not need to be reamed to fit the shaft.
The oil seals are 1.124" O.D. and 0.625" I.D. They are easily obtainable at Bearing Specialties, Kaman Bearings, and any similar bearing suppliers in the USA and elsewhere. Depth doesn't matter provided there is space between the two seals to allow water to drip out the weep hole. The part number I used is "C/R 6229" which is a double-lip seal. (The original 5411 documentation shows only one oil seal.) Press the inner seal all the way into the bore against the seat. I use a 13/16 inch deep socket as a press tool. Orient the seal so its metal side is inward toward the impeller.
Then press the outer seal into the bore with its metal side outward away from the impeller. To avoid pressing it in too far and covering the weep hole press it so that the seal is flush with the surface of the casting. Lubricate both seals to avoid possible damage during shaft insertion. I use spray silicone lubricant.
Install the impeller onto the shaft with its key and C-clip. then carefully push the shaft into the bushing and through the seals, rotating it while pressing so as not to damage the rubber seal surfaces. I spray silicone lubricant into the cavity before closing to keep the impeller lubricated when the pump first rotates after it's reinstalled on the engine.
Shaft extends through the rear oil seal.
Front cover shined up and installed. Stuff works better when it's clean!