When do you rebuild or replace a water pump. The one in question is less than 4 years, low mileage. Impeller looks good but realized yesterday the sea strainer was backward, and engine over heating. Took apart the pump to check impeller but the pump metal looks awful impeller fine ther is probably rusted grit in the bearings? I replaced the port side last year, just wondering if there is a rebuild option rather than new pump. Mechanic had put the pump on backward, makes me wonder about the sea strainer. Doing my own from here out.