Raw Water pump failure in FWC system

[Tom Witzel]

My Atomic Four is FWC with a Jabsco model 1673 series raw water bronze pedestal pump, installed 2003, newly purchased for $200. After about 150 hours of engine use on it, a lot of water started spraying from the gap between the spinning and fixed portions of the pump. I removed it and found that it spins easily, that the (new this season) impeller is fine, and that there are no leaks from the cover plate. I removed the pump from the boat and removed the pump shaft. The shaft(bronze) was tight in the pump head (aluminum!). The rubber seal sheds easily when scraped and the seal casing appears loose. The belt tension was not excessive, being easily deflected 3/4" between the 2 pulleys. I sail this boat, a shallow draft keel/CB, in the Chesapeake and occasionally may be under power in muddy/sandy bottom, particularly if I have run aground. One thought is that I have "ground up" the seal with sandy water. Has anyone else experienced premature failure of a Jabsco 1673?